Most people that one would describe as evil do not see themselves as evil, but rather see what they're doing as justified. Saying you're not going to be evil means literally nothing.

Don't be the bad guy, ok, but if you think your goals are noble enough then crossing lines becomes acceptable. Google sold everyone on the "we're going to change the world for good and improve everyone's lives and make all information accessible and free" line, and in doing so justified everything else they did - privacy invasion, monopolistic behavior, etc.

The fact that they said "don't be evil" should have been a massive red flag for everyone, not a green one.