If an artist or singer did something bad, should we stop appreciating his work?

But yes, if an artist's malevolence bleeds on paper or on tape(such as singing about commiting felonies while actually being a criminal), then discretion should be taken accordingly. Such cannot be said about the relatively neutral and un-violent paintings of German buildings by the aforementioned guy, that is why we do not consider them exceptionally ugly at any time.

But if one's artwork is mere propaganda(such as advertising for an evil corporation via graphic designing to lure people into "donating" money), then discretion probably should also be taken appropriately regardless if the person who made it was evil or just hired with money.

I know this example is either cheesy or inappropriate, but go find me a better example if you do or will. I'd rather not google extensively on how much art someone did at an airport.