There are much more effective ways you could protest the TSA. Mouthing off to random employees in a grocery store was clearly not chosen based on effectiveness but laziness, so don't lie to yourself about the lack of venues. It's cowardly because you wouldn't use fighting words like this in a context where you believed they might respond like many reasonable people would: with a punch in the mouth.

You're hiding behind their own civility and restraint. The same way many women think they can freely attack a man under the assumption that many men don't want to hit a women. It's cowardly to use someone else's self-control as a weapon against them.

And you should realize that your personal opinion that they're fascists and child molesters is not even close to a proven fact. It's a slanderous and exaggerated characterization that very few reasonable people would agree with, even those that do not like the TSA at all. Try reporting their "child molestation" to any law enforcement anywhere in the world. No judge and no jury would convict them of your charge. It's not so much different from calling a doctor that checks a child's testicles for problems a molester. Context makes all the difference legally and ethically. You disagree with the ethics but that doesn't make you right. Legally there's no question that you're wrong.