Film them, photograph them, expose them. 

By "them", I mean the Leftards that will infiltrate a Tea Party protest, and shout racist remarks.  Or who will encourage violence or vandalism.  It has always been the Left that was comfortable with violence, racism, and vandalism at its gatherings and protests.  And it has always been the MSM that was sympathetic to those on the Left who did such things, in the name of progressivism. 

Having seen how effective it's been so far to have their Democratic congressmen crying like little babies, the Left will, following Alinsky's rules, use more agents provocateur.   Given how in-the-bag the media is for Obama, it is also likely that there will be a prior arrangement between the Leftard and the media to have a camera on site, rolling at the exact time and place necessary to get it on film.  

How to defeat that?  With our own cameras.  Our own research.  Our own media.  Take a video of everything.  Miss nothing.  But especially video those who appear to be encouraging violence or vandalism.  And especially those who appear to be shouting racist remarks, and who are surrounded by MSM cameras and microphones.  With very little research, it is likely to be found to be someone in the employ of SEIU, or ACORN, or MoveOn, or the DNC, or ANSWER, or the White House (not that there is any real difference between any of them anymore).  If they aren't in their employ, they will likely be at least supporters of one or all of them.