Zu wenig Kontext, um sehen zu können, ob das gemeint ist bzw. ob sich das "artsy" auf den Slum als solchen bezieht oder auf die Tätigkeit des Dort-Übernachtens.

Slumming means to do something or go somewhere that is lower class than your normal life, usually out of curiosity or with a condescending attitude. For example, to go to a dirty bar in Williamsburg instead of the fancy bar in a Manhattan hotel. Artsy slumming probably means going to dirty bars in Williamsburg where the usual customers are artists, musicians, writers, etc. or people who like to pretend they are. To spend a night or two doing this does not require an overnight stay. One could make several one-night trips. I am sorry that I do not know the German term for slumming.

Solle sich aus dem Kontext ergeben, dass die Sprache etwas rauher ist, so kann ich auch folgende Übersetzung vorschlagen:

"to be slumming" can also mean to have sex with (mostly) or date someone who is considered having a big lack of beauty.

The addition of artsy could be used for ironic matters, because you probably won't find that much art in having sexual intercourse that way.

I agree with FredM's discussion of "slumming." Not at all sure about Mard.at's point.

"Artsy slumming" could very well be what FredM guesses.

However, without knowing more precisely what the speaker is referring to, it is hard to be certain. What was the activity engaged in in Williamsburg?

es abwerten, auf ein primitives Niveau ziehen.

...und was heisst's nun auf Deutsch?