Losing close friends over any issue is a sad fact of life. Families were split, and remain spilt, following the miners dispute. Sad as it is doing what you consider to be the right thing for you is the only way of approaching the issue. If close friends see that as an issue over which they are prepared to bin a long friendship then that is, unfortunately, life.
I would, however, question my definition of a close friend if they made threats to 'never speak to me again' if I didn't behave the way they wanted me to.