Virtue signalling is usually done by people who sincerely believe the values they espouse - but they emphasize or show those values in order to gain or reinforce social status within the group. It usually is done by proclaiming things you hate, rather than things you like.

If the comment adds nothing besides an "I'm with you guys, that's the worst", it's fair to see and describe it as virtue signalling.

And yes, it happens on both sides of the aisle - heard lots of conservatives proclaiming their distaste for Obama over the last decade.