Do you use auto-tune always, no matter the context?

Ok, so I'll start by saying that by no means I'm professional. Just a guy who mixes songs for his band, so I could use opinion of professionals.

Recently the lead singer said that I should use auto-tune on songs always, no matter what song is it and is vocals noticeably out of tune, and It makes vocal sound better no matter what. Also his friend who's in a much bigger band says the same. I feel that having auto-tune on soft, emotional songs lessens the impact, and I'd rather do a punch in or comp if something is very out of tune and leave small imperfections as it feels more real to me. What do you think?