I think you may be underestimating the number of agents who have been thrown up on. (And the number who have had to call for cleanups for vomit that did not land on them, and medical personnel for the ill traveler, is even larger.) The thing is though, that's what they signed up for. If they can't handle vomit, they should look for another job.

From a certain point of view, it's better for the TSA agent to be soiled with vomit than it is to allow a potentially contagious passenger on what may be a very long flight.