I sort of want to call still vs. this player type. Maybe it's too weak and it really sucks when we lose to 84 but whatever, a fishy player taking a BxB line with less than 1/2 pot on the river I have a hard time folding any showdown value.
This sizing from a fish doesn't seem very bluffy to me. When they go a little under half pot, I feel like they usually have something marginal that is trying to get hero called. In this case, a marginal hand might be any random non-nut flush. A bluff raise seems pretty suicidal since loose fish suck at folding. I just let this go and don't worry about it too much.