I don't think the need or desire for security and impinging on the right to film in public places are necessarily correlated. At least I sure hope they're not. I think the question is, according to your line of reasoning, to what extent does public video and image recording impede the functionality of the TSA to provide security? In my opinion, it does not affect them adversely enough for me to trade the surrender of liberty for the safety and security they purport to provide. Just my opinion. It's a debate that goes back to before the Constitutional Congress when the country was being created.
I personally think the TSA is ineffectual, moot, a waste of a billion dollars a year, and primarily set up to 1. acclimate people to the creeping police state and 2. give thousands of people jobs in a time when real unemployment in this country is somewhere around 15-20%. But that's just opinion. I honestly think that the success of the TSA in doing their job, whatever you think of it, is not so adversely affected by people filming and taking pictures that they must no longer do so.
People in positions of power generally don't like when the spotlight is shone back on them. That's nothing new.