So, which part of them is innocent? Hired killers for money who kill "problems" for whomever they deem to be unworthy to live. That is who the Gur are.
The Gur were never innocent. They were monster hunters and didn't ask questions about whether or not if you were in fact a monster who did something outside its nature.
Did Astarion want to do what his master bidded? Did he have a choice? They KNOW Astarion did not have the option to refuse Cazador's orders.
In my opinion, they are rude and judgmental for their OWN reasons & beliefs. If you do not want to help them with their war, you become another "problem" and attack us for their own judgemental beliefs.
So since we did not participate in their beliefs and were rude going about their asking, the Gur simply attacked the party and we simply defended ourselves.
OK, I see the denial is strong again. Gur are foremost tribes of wandering people, similar to the Sinti and Roma in our world. They have their own culture and customs and are not evil in DnD lore ( unlike vampires, I might add). The Gur in the game have all the reason in the world to hate Astarion,since he stole their children. But they listen to reason and even team up with him to bring down Cazador. Of course, they have a problem with Astarion sacrificing their children to an archdevil ( and please educate yourself about what it means, becoming an enslaved soul to Mephistopheles, he is notorious for his magical experiments - and we are talking children here), it means, their souls are lost and condemned for eternal torture. If you like AA , great, but please don't alter facts to clear your conscience. The Gur in the game did nothing wrong.
"We are all stories in the end. Just make it a good one."