Hey Dee!
I came across a great quote the other day online which is I feel is relevant to this topic:
“Before you diagnose yourself with depression or low self esteem, first make sure that you are not, in fact, just surrounding yourself with assh*les.”
― William Gibson
Sorry for the language in that quote, but I find its something that is very true. (And something which I remind myself when I come across really unforgiving people).
I think you should stop looking for the negatives within yourself because you sound like a very lovely person and a good friend to have. Your "friends" who defriended you however, sound like the complete opposite.

For someone to defriend you after 15 years of friendship for a political comment... I think that shows more a reflection of their character and intolerance more than anything.
I think you shouldn't dwell too much on what has happened, but rather look to the future and to all the new friends you can make in due time. Also appreciate the great people around you, like your DH and family. Like everyone else has said, it's really great you're making lots of progress in your weight loss... those who don't want to share your happiness probably don't deserve half of your time. (Just my opinion).
Stay healthy and happy!
