This assumes that he was not picked by random but instead there is some sort of list of people to check at airports that you can be put on because of your work within IT-security.

That would be a big story if that is the case.

I will offer a counter-narrative which is more in line with my own experience (from other places than the US):

The people who work at border control in particular in airports are bored.

They are also overstaffed and given extreme discretion over the people they patrol; most of whom are non-citizen and thus have basically no rights at all.

This leads to them doing work for the sake of showing they work, overreacting to the least of resistance and maybe even some games of entertainment.