I think in some of the internet people are beginning to demonize Chick-fil-a just a little bit too much. People like this guy who lost it with a Chick-fil-a employee are doing more harm than good. If you want people to support your cause you have to distance yourselves from people who are obviously not helping and condemn their actions, even if you agree with their message.
Dan Cathy is the President of Chick-fil-a and he dislikes gay people and thinks horrible things about liberals and whatever. So that's fine, if you don't want his company having money, use the Free Market to your advantage, don't get food there and do your little part. But I can almost guarantee you that yelling at an employee at Chick-fil-a, or vandalizing a store is going to rally the Right to their cause more than it's going to make people think about discrimination.
The average employee at Chick-fil-a probably doesn't know, or care, about the president of the company. I have, in the past, worked for a couple of different fast food places and I never had any idea who the boss of the company was or what their politics were and I was fairly involved in such things. I would guess this holds true up until the corporate level as well, so destroying a store, or yelling at the staff isn't going to make anything better, it's just going to ruin someone's day, or worse, make them think that people who support gay equality are terrible people and therefore gays must be terrible people too.
Look at the way that the news is dealing with this issue now, it's gone from a protest against what they do with their corporate money, which everyone I think agrees isn't illegal or somehow dishonest, to a media story about how 'the gays' are being disrespectful, causing damage and generally doing exactly what we would scream at if the Right did to Ben & Jerry.
Do unto others as you would have them do unto you. If you want other people to treat you and your ideas with respect, you must disagree with their ideas respectfully. I'm not saying don't protest legally, or that this is an issue that should be ignored, but if you're doing something illegal, or heck, just mean, you are NOT HELPING, you're just providing fuel to the fire and allowing Dan Cathy to look like a victim of attack from the evil liberals and if media goes with that meme, and we keep providing them evidence to support that meme some people who were on the fence are going to get off the fence.
Some will get off the fence to come support you and your cause. The problem is that some will go off the fence the opposite way, to get away from you, and when that happens there's nothing you'll ever be able to do to convince them to support you again and you've lost a potential ally just because you wanted to be an ass to a $8.50/hr fast food worker who's never heard of Dan Cathy and doesn't care.