I don't know if it's a violation of freedom of speech, the only problem i see is that the pastor is suppose to be the 'mouth piece of god' on Sunday morning. That power seems like it's being abused if it's being used to promote one's personal beliefs on politics.
That's not to say a pastor can't come out to say who he's voting for, but there is a time and a place for that. 10 o'clock Sunday morning isn't the time or the place.
If you're going to church to be a good christian,  you shouldn't be subjugated to the stipulation that a good christian is a Republican christian.
Individually you can combine your faith and your political beliefs, but i don't think that it should be done publicly, I'm sure there are plenty of impoverished church goers that would vote for Obama purely for the tax relief they'd receive,  but have their minds changed because of 'religious' reasons that wouldn't affect them at all, (ie. abortion rights) due to a churches influence.