Ask

I do.

Some of the works I admire the most have been written (or painted, or composed,...) by people I don't like, to say the least.

Humans are complex beings.
Culture, social norms (good vs bad) and historical background (what was considered legal and illegal) are also very complex. And the can be very different from one region to the next, and even in the same region from one time period to the next.

While, on the other hand, the action of judging someone else (or some past time) is often lazy as fuck, based on nothing but personal emotions (hate, anger, sadness,... or their exact opposite), distaste (I don't like to see/hear/taste this or that) and preconceptions (I think people should (not) be allowed to do this or that).

You don't believe me? Well, you're absolutely right to not believe anyone, me included, but then just go ask a few racists out there how easy it is to judge (and to hate on) someone based on their race or skin color, or even on their culture and social norms being different from ours... Do we really want to act like racists? I certainly don't, even when it's for other reasons than race, even for 'moral' reasons. Which, btw, is in itself a very changing notion.

I also think no one, me included, is perfect. So, how come should I be allowed to judge and to condemn anyone based on their own imperfections and faults?

Judging should be the job of the judges: people that been educated to fairly be judging (aka by accepting as a fact that anyone accused of anything should be considered innocent until proven otherwise) people's actions based on a set of arbitrary rules (that is the law) and when deemed necessary by punishing anyone that has not respected said rules. Judging should not be my job as an individual, filled with my own emotions and personal biases, nor as a citizen with my own set of values, and it is even less so as an amateur of art (no matter how deeply I may (dis)like some artists).