A friend asks if it is OK to be angry about a relative having "chosen" behavior that has led to his imminent death and a lot of grief for those around him.
You have an absolute right to feel angry; in fact, you don't have a choice. Anger is an emotion, and it will happen whether we agree or not. If we try to suppress emotions completely, they always come out in other ways eventually. We can moderate them when we need to for social reasons, but we have to allow ourselves to feel and walk beyond them.
Once your anger has discharged, you will probably find it easier to appreciate why people with various compulsions do things the way they do -- whether or not you come to understand it. The one thing you must understand now is this: working through the anger (and, yes, the grief) is something that you have to do for yourself. It is not about loyalty, it is not about propriety, it is not about right or wrong. It's about dealing with an emotional upheaval of mythic proportions.
I tell people that it's like taking out the garbage. If you throw the bag in the pantry instead of taking out the trash, eventually cleaning the pantry becomes not only a nasty job, it becomes imperative -- otherwise, stuff starts leaking under the door and ruining things in the kitchen.
Be angry. Yell, scream, and don't feel guilty about it. After that -- and it may take quite a while -- try to come to understand, for your sake as well as that of the others who may remember him differently.