Well, being angry at them only serves to hurt you. Now is the time to use all your energy to look after yourself and help yourself recover and survive your cancer, instead of worrying about them or their shunning. Why would you give up now and, in effect, let them win? Why give them an opportunity to say "My dad left The Truth™ and Turned Gay™ and got cancer and died. That's what happens when you leave The Truth™"? You know that is what they'll say. You know that is what they'll think. This is your chance to show them how wrong they are about you. This is your chance to really live and fight for your life and survive. I know you can do this because you have people in your life who do care about you and who love you and who want you to stick around for a long time.
Let me also say that anger is a normal part of the emotional response to a life threatening illness. You have every right to feel that way, but try to find a way that channels your anger into fighting your illness instead of harbouring grudges against people who have hurt you. Maybe your anger about your illness is being directed at a very easy and most obvious target: family members who shun you, instead of toward the illness/diagnosis. I hope you'll take some time to reflect on your emotions - even if you have to write them in a journal - because that can be very helpful in unravelling all the mixed up feelings that we experience during times of chaos and emotional upheaval.
Do remember to take care of yourself, and let other people care for you too.