I voted conditionally. Sometimes the punishment 'doesn't fit the crime."
However, if they keep coming back and littering the good forum here with garbage and other inappropriate, unrelated stuff then ban again. Then delete the content they posted.
I cite the crackdown on graffiti in the subways of NYC in the 90's. If the artist's paint is gone almost immediately and no one sees it... it's not art, or appreciated. There's no more motivation, so the graffiti stopped (mostly).
It took a lot of work, also making sure there are people to remove the graffiti. However, it paid off. Unfortunately, I think it may mean the same at the forum.