Horrible events like hijacked funerals are reminders that, as members of a misunderstood minority, we need to take responsibility for planning our own memorial services.
Write your own obituary (update it annually) and file it along with your will. Document your wishes for a non-religious event, pick the person to deliver the eulogy, select your own secular readings and music, and clearly explain all these things to your family and friends. When you're gone and they're suffering from your loss, the last thing they need is an insult to your memory from some fly-by-night-friar-Tuck who thinks he can get the last word in because you're no longer able to correct him.
[update: typo fixed]