I'm all for creative, anti-Democrat t-shirts, but this is a little much,

There are certain things that should be avoided in politics and one of them is jokes about assassinating people on the other side of the aisle. Sure, it may just be a goof, but it's inappropriate given that every so often, deranged people actually try to do this sort of thing (See Ted Kaczynski and the loon who walked into a Unitarian church and started shooting to name two examples).

Are they going to do it because they saw a t-shirt? No, but t-shirts like this do give some people the false impression that sort of thing is being winked at when it's actually almost universally condemned on the Right and, to a lesser extent, on the Left.