To a decent extent, statements like this are designed to get himself some ink on a national stage, and throw his name out more on the national spotlight. He knows perfectly well that the chances of SXSW listening to his request are somewhere between slim and none, but at the same time, he can use this to help any claim he wants to lay that he's tough on terrorism and national security. Wouldn't be surprised if he's planning a move for senator or governor in the near future.

I think you underestimate the extent to which SXSW has gone mainstream. There are likely a lot of conservatives who deplore Snowden's actions participating in SXSW.

Congressmen like Mike Pompeo sit in the House of Representatives, which governs the whole US.

Rep. Pompeo is on the House Intelligence Committee. He most likely honestly hate what Snowden has done and represents a part of the country which is very anti-Snowden. This is easy grandstanding for him.

He's misguided, in my opinion, but that's "why".

I think the congressman knows he can't single handedly stop Snowden from speaking. But he can do his part to contribute to an atmosphere of pressure against Snowden speaking to nudge the probabilities in his preferred direction.