In short ,Horde was/is hostile to the Alliance and a great to threat all races in the game. Races of the Horde brought nothing but a doom ,destruction ,corruption and invasion with some of minor exception. I don't want to go into deep but into a close analogy to the real world the Horde represents non good will people ,demons as well tribal clans
"After reading a book not related to WoW. He closes it and sighs"
Both Sides:
Horde, Alliance... both are hostile and both have grave past mistakes. Horde is not a great threat to all in game. They are but a family. They were lost and found their path back to redemption. They were evil once, but wait, no, I disagree to myself too. They were just mislead and misguided. The Burning Legion manipulated the orcs into invading Azeroth. It wasn't the Horde who said "Hey, lets invade a world, shall we?!". It was those who failed to lead them and people such as "Gul'dan" that were blind and consumed with power. You see the Horde as devils. But do you look at the Alliance at all? There were many orcs that rebelled against this demonic rule. Just as many humans rebelled in the past against their own human nations and then separated into many kingdoms of their own. It's war, man. Also, there are similarities to both Horde and Alliance.
Alliance are Evil too When it Comes to Things Such As:
1. Gilneas sealed themselves off as cowards and abandoned their allies. What kind of people could of done this to their own kind?
2. The Horde were manipulated by demons and lead an invasion to Azeroth. The Alliance were manipulated as well by even Deathwing himself. Sure, the difference is between damage they both caused. But still, if I manipulated the Alliance and caused Azeroth's destruction. Would you still view them as demons as you do the Horde today?
3. When the Kirin Tor found out that they could cure the orcs from what the demons have done to them. Most of the Alliance's leaders then resigned from the Alliance, pulled back their kingdoms, and abandoned their nation due to one idiotic thing? Instead of finding a quicker way to peace. A quicker way to solve issues. They instead enslaved, spat, and broke the spirit of all orcs. Alliance, like the Horde, were filled with hate in the past. The orcs liberated their own kind and even sent a message to the Alliance. Free all the orcs and peace will be between us. Did the Alliance accept? NO! Old hatreds.
4. The High Elves refused to train rangers and allow their allies to be experts as rangers like them. What kind of an Alliance is this?
2. Blood Elves:
And now on to the greater things. In another topic. I saw you say Garithos is a hero? Excuse me!?
Lord Othmar Garithos was an extreme racist. He hated the elves because they failed to defend a town he lived in when he was small. When the time came to restore the Alliance's greatness. The Blood Elves did thirst for magic, but not even for a SECOND, a SECOND did they thing of finding a cure such as fel magic. Lord Othmar Garithos lead them to that dark path when he spat in their faces and pulled back an entire support force. With this, the Blood Elves had every right to leave the Alliance and do as they please. If you were being oppressed. You'd do the same thing. It was Garithos' fault for the Blood Elves' status today, but the Blood Elves that apart of the Horde, if you didn't notice, do not serve Kael'thas. There for they weren't related to the demons destruction any way. Most Horde Blood Elves were those that remained back at Azeroth that joined the Horde. Garithos wasn't a hero. He was a "fool" and he let his hate, his racism, be the doom of the Alliance.
3. Darkspear Tribe:
Now tell me? How exactly are they demonic evil related? I mean, they never battled on the demon side. That were Forest Trolls and if I recall correctly. They battled Garrosh Hellscream when the time was right and took care of their family. In conclusion, how are they evil? Because of one leader's idiocity?
4. Tauren:
How... are... they... evil? Do explain? What have they done wrong? The Grimtotem Tribe have done wrong, but wait! They're not apart of the Horde. The Tauren are peaceful and loving creatures of nature that joined the Horde whey they helped them. They never wanted to cause destruction and they battle only to protect their loved ones. If this is evil and if this is a crime. Then lock me up. I'm evil.
5. Goblins:
Explain how they are evil related? Maybe they are intelligent, filthy, and greedy. But I don't see any evil in them. It was the Alliance that raided their homes and attacked their ships without warning. It was the Goblins of Kezan that joined the Horde because they needed help. So, I ask of you? WHY!? Why are all the Horde evil to your eyes?
6. Forsaken:
Now this band of people were once apart of the Scourge. Garithos was around when they took Lordaeron, yes. It was Sylvanas that said she'd kill him before even the battle over Lordaeron was won, true. But even here Garithos shows hatred to someone and proves that even the Alliance are savages in mind. "Now, get out of my city before I..." His last words and I'm glad they were. He brought shame to the Alliance. The only evil in the Horde AFTER the second war I saw from Sylvanas. And don't say what you will say later. Yes, they invade Gilneas, Andorhal, and more. But in a vision. The Alliance raided Lordaeron and showed no empathy. In war, no sympathy and empathy must be shown in battle.
Conclusion:
In conclusion, both sides have their past faults and future faults. But in my opinion. You have no right to call the entire Horde monsters because of the demons that manipulated them and the past orcs that were consumed with power. Goblins, trolls, and blood elves suffered from the Alliance and their betrayal. During Garrosh's rule. Most members of the Horde rebelled against Garrosh and deep down inside even then didn't care for the war because all they wanted was to secure their family first. The Alliance did nothing but hate them during the war, while most members of the Horde tried to forgive (Except for the orcs under the Kor'kron). So, you can take your opinions of hatred and shove them back into your mind. Read about both sides and know that you are just thinking of the Alliance. Think of the Horde as well.
P.S:
Apologizes to Sir Razosh. I know you probably didn't want this topic to turn into a flaming war one. But defending is my thing. Also, this topic has gone WAY OFF-TOPIC.