Yes, it is difficult to be friends with someone who disagrees with my political views, because it is so easy to argue with them. Often, what starts out as a conversation about one thing turns into an argument. It is hard to talk to the person about what they want to do with their lives, because it is hard to understand their point of view.
I enjoy discussing differing beliefs with opposing viewpoints, but this (though exhilarating) is exhausting for me if done on a regular basis. Also, in my opinion, friends should be there to support you no matter what, and I have found that opposing beliefs,often get in the way of unconditional love. Of course, thIs is not to say that I dislike befriending people with different beliefs (I personally seek out people with contrasting views for the interesting conversations we have) it's just that being friends with opposite minded people can be trying, and can lead to a stressful relationship. Open big plus is that you learn tolerance of different beliefs!
I do not find it hard to be friends with people who think differently than I. I can get along with just about everybody. Some of my friends hold different beliefs than I do and we have a mutual respect for each other. We can get along even though we share different view points. We see the good points in each others arguments but when it comes down to it we hold different views.