Amazingly since I've been out for 15 years, I've been so blessed to be surrounded with loving, open-minded people everywhere within my family, friends and work. I've never lost any friends or family members because of it. My family is so supportive of gay rights that they all voted No on Prop 8 even if some of them were Republicans.
If people are losing friends because of who they are or for standing up for gays, that only shows you the type of people they are, that they are closed-minded and judgmental. So in the end, its all good because its way better to surround yourself with people that love you for who you are whether gay or straight, but accept and support your beliefs.
As for family members that reject others because they are gay, of course that is tough as family is so important. I think that there are some ways to work around this. We can't change them for who they are, but as long as they are family, the love for them is always unconditional. It shouldn't be something to pick a battle with. Rather it should be a lesson in acceptance, tolerance and forgiveness. I have one relative that was against me being gay. She was the only person in my entire life that was not accepting of who I am and tried to tell me her own thoughts about it via email. I shut her mouth on that issue. So if I see her at family functions, we are still loving relatives, only we don't bring it up. It's left alone. It's important to my family there is peace not conflicts as it won't accomplish anything.