No, 'nasty things' is not the way to go. It's important not to come across looking juvenile or nasty.

Just tell it like it is. HSUS misuses their funds, HSUS does not fund local shelters, HSUS aids domestic terrorist groups, and HSUS has proclaimed its goal is to end the private ownership of reptiles in the US.

I've already gotten a few people to stop donating to HSUS. The more folks who spread the word, the heavier the impact will be.
Search YouTube for more fuel for the fire. HSUS has been a bunch of BAD boys. They really have. They've had news features devoted to how naughty they have been. They're in a bad position to throw stones, we just need to publicize it more.