Nowhere was it written that the orcs were forcibly converted. The naaru showed the draenei what the orcs (and the world) would become if left unchecked and the draenei declared war on the orcs to save the world from the orcs. Out of charity, they offered the orcs a chance to convert and some did, the rest were fenced off in gorgrond which is now a junkyard wasteland thanks to the orcs destroying the environment. If you actually read the text, all the dranei care about is racial harmony and getting rid of the global warming caused by the old iron horde industrialization.
The orcs then claimed the non-savage orcs were brainwashed, as they cannot understand why anyone would leave the orc master race otherwise. It is not hard to find real-world examples of this same sentiment. This is where the derisive name “lightbound,” as if they were slaves now, came from.
The orcs accuse the dranei of being “fanatics” (that word is thrown out every sentence by genderbent thrall), yet it is the mag har who scream “I will destroy all who oppose warchief hellscream!” in their flavor text.
They claim the draenei want to destroy all different from them, when the first part of that scenario is ethnically cleansing ogres because they dare stage a slave uprising and then there is a lot of flavor text about killing lightbound orcs because they are race-traitors.
The reason you go kill the ogre slave uprising is because (and the game outright tells you this) slamming the jackboot on the ogres calms down genderbent thrall!
I could go on, but I wrote a detailed, play-by-play of that scenario here and would just be repeating myself:
But this is my point in the OP here, because the orcs are played straight as evil people are, they are taken at face value without question. The mag har by action are oppressive psychopaths, but by rhetoric are some oppressed group of heroes. So they playerbase ignores all that the mag har actually do because they could never imagine the mag har are liars.