It would be naive to suggest that isn't exactly what's been happening.  We saw it in 2009/10 with the Tea Party, and now liberal activists have perfected the technique even more.  They wave their signs and shout down the Congresspeople, intentionally making a big scene so that TV crews will show up to the next one to see if it happens again.  And it does, and they do.  It's free media coverage for their political agenda (i.e. to embarrass the Congressperson in hopes of damaging their chances of reelection).  It's a political stunt by the opposition.  They're gaming the system. 

Now, that doesn't mean EVERYONE attending is doing it, of course. The activists are actually ruining town halls for those regular folk that show up to have a calm, reasonable exchange with their representatives.  

There are many ways to contact your representative. The fact that the opposition complains so much if it's not a town hall (where they can gang up on) just further proves the point.