"evil" doesn't mean anything.
The Daleks are xenophobes.
Their end game is to be the only life form in the universe.
After they discovered time travel, then they wanted to be the only life form ever.
Then they discovered mirror universes... Well you get the point.
NonDalek lifeforms are a sickening abomination that have to be put out of their misery.
They have a clear and present agenda no different from when they were the Kaleds, and frankly little different to how the Thals thought either, so factually they are are just following their bliss.
Although bliss probably doesn't exist either.