The problem is that it is hard to prove anything...

The TSA staff are "trained" to spot people they feel are more of a security risk than your average passenger, and frankly someone acting hostile or difficult could easily be put into that category.

For example, if an old person complains about having to take their shoes off (as many do) they aren't going to get hit by a secondary screening. But if a twenty something decides to throw up a big fuss then the TSA are likely going to assume that passenger is acting in a suspicious way since 99.98% of people don't do the same.

In my experience is it almost never a good idea to complain to authority figures at the time and instead save your complaints for a later date. This is particularly true with the police, just hush up and raise your complaint to their superior later. Fighting them directly only leads to escalation...