I'm going to criticize my friends art
Do you think it is bad or offensive?
Of course. I don't believe in her art at all. No one likes it.
It's fine to not like someone's art. It isn't fine to put someone down because others do for enjoying a hobby.
I am not putting her down. I just don't agree with her talent.
It can be really hurtful if you say you don't like it in a mean way. I think you should be honest but respect their feelings and interests.