I agree with the other answers - true friends accept you for who you are and are happy that you are happy. If they can't, then they're not as close friends as you maybe thought they were.
Set some boundaries, and limit how much they are in your life. Maybe they will eventually see that this is a serious thing after all and that they were wrong, maybe they will drift away.
Friends are our support mechanism, sometimes more than family - it's really important to have friends who support our happiness.
Please check out The Birdcage - an open, friendly Polyamory forum for all parts of New York State
"Listen, or your tongue will make you deaf." - Native American Proverb