The most important thing about making a massive, angry showing at these townhall meetings is that the politician gets the message that we are paying attention and we vote.
Exactly. There is an extrapolation by politicians that for one person who writes or calls their offices to express an opinion, there is X number of others who think the same way, but don't write or call. I'm sure it is similar with public meetings, which take even more effort than just typing a few sentences or picking up a phone. The effort is not lost on them.
For those who duck and hide, the consequences will be even more severe. They have surrendered a major point to any future opponent who will drive the point home that they are cowards and do not care about the opinions of their constituents.