I agree very much. When I make a question of how I look, I expect honesty, not for you to stroke my ego.
Not everyone who asks a question actually wants to hear the truth. However, in your example, if someone asked me what I thought of a particular outfit they were wearing and I didn't like it, I wouldn't say it's an ugly outfit. I would probably say that another style might be more complimentary.
I don't ever have an opinion on material stuff. I never look at an outfit or hairstyle or face and think "I like that" or "I don't like that".
So if you ask me if I think your butt is big I will likely offer to sex you up.
I have lots of opinions on ideas and I will always tell the truth on that.
That's a good way to think!