While this is an interesting comparison, I don't think it's particularly relevant.

First: the threat model at play is different. Nobody's concerned about someone hijacking a courthouse, transporting it to a different state, and blowing it up there. A courthouse is a stationary target; the type of damage that can be wrought is qualitatively different.

Second: the nature of people's use of the courthouse is different. One of the arguments frequently heard in TS&S is that no-one is forced to fly aboard a commercial aircraft. (Largely, that depends upon one's definition of "forced", but let's set that aside for the moment.) In contrast, one can certainly be compelled to appear at a courthouse, under penalty of imprisonment (e.g. for contempt of court). At that point, since people can be compelled to submit to security procedures, one must take greater care to respect their civil rights.

To be clear: I'm not convinced that TSA's procedures are effective, or appropriate. But comparing TSA checkpoints with courthouse security seems to me to be comparing apples and oranges. I think there's plenty of room to criticize TSA on its own merits, without having to make comparisons to other security systems.