With recent events and the way things appear in 5.1 to come, the line between what is right and what is wrong is becoming thinner and thinner each time something occurs.
In relation to the horde, this line goes with several characters and actions that demonstrate the how these things work, but if you take the time to step back and actually look at the situation now, with an unbias look at events, you discover how there is a forming set of standards within the faction itself, growing more apparent in coming events involving Garrosh and 'his horde'.
What I've gathered of the way the devs are moving things along, this is how it may look by the end of the expansion for the horde, a split between the good side of the horde, and the bad side.
The blood elves
A handful of orcs not following Garrosh
The majority of orc grunts
Rogue Blood elves working for Garrosh
Warsong devoted orcs
Blackrock orcs being brought into this horde.
And of course, there are the forsaken, who lets face it while they don't seem to want to follow any of Garrosh's ways, you can't call the forsaken good in any sense of the word, so while they don't fit into Garrosh's mentality, they can never be trusted either. At this stage of the story, what the forsaken are doing pales in comparison to what Garrosh is doing, so they might be an ally to the horde when it comes to fighting him, or they might not.
While the good element of the horde seems to outnumber the darker element of it, in its current form Garrosh holds all political power from the other leaders, and if any of them act against him, he would use his insanely devoted followers to slaughter that leader and all there people. He's already shown his insanity in trying to have vol'jin killed and having the kor'kron lock down the darkspears and keep them capture.
Now there might be someone who thinks 'yes but <add horde race> attacked the alliance', but if you consider that without being a bias fan for a moment, did they attack the alliance because the alliance threatened them, or did they do it because Garrosh threatened them to do so? That is where the line is drawn for many horde races atm, who are held under the command of a twisted leader that forces them under penalty of death to obey everything, even if they (like the darkspears and tauren) don't want to.
In its current stage, the horde is held by the darker element of it, yet we all know this is set to shift in times to come soon.