They didn't understand what the Naaru was and many blood elves did not approve of what was going on.
IIRC, they only burned one church and it is canonly still standing.
We have no idea how they supported the bombing of Theramore, we know some did, only the siege.
Did they do the same thing that Arthas did? I fail to see the scourged land leading up to Teldrissil. They were assuming they were going to capture the city, not raze it?
Don't assume everything the player means that they supported it.