If they had used Campbell's soup can, at least it would have raised a question about Van Gogh vs Warhol vs Pollock.
I think this kind of protest is in "bad taste" - not because I dislike tomato soup - but because it gives others ideas who misunderstand the point and are less careful.
That said, many people who are upset over this seem to miss the point that it didn't just fortuitously happen to have a glass protection, but rather that was essential to the protestors' message: that we protect our valued things from assault, but we don't protect against the risks they are protesting over.
From my perspective, the core problem of the event is zero alignment between the action and the cause they ostensibly champion. Their actions thus become arbitrary and their message obscured, despite the obvious publicity. The net result is a stronger signal of entitlement and weak reasoning than nobility of cause.