I am a Ms, and I've had a lot of flack for using it over the decades which has hardened my determination to use it; now I'm adamant.
Ms is short for 'Mistress', just as is 'Mrs' and even 'Miss'. The title 'Ms' is pronounced 'mizz' and it's been around since the seventeenth century, so no one - but no one - should have a problem with its usage.
I did not change my name when I married - but I had already changed my name when I finally went NC with my family of origin. I didn't want my father's name, so I simply used my own birth names from that point on.
Funnily enough, I've never actually come across the 'divorced' label being ascribed to my usage of 'Ms' (or maybe I just haven't been aware of it?). However the 'radical feminist' and/or 'lesbian' yes - and how. I've got very short hair, as well, which possibly inclines some people to assume one or both(!).
I do care; I care very much. People trying to force me to say whether or not I'm married; people refusing to use the title I have chosen with consideration; people threatening me with various sanctions for not changing my name to my partner's or refusing to state whether or not I'm married (where a man wouldn't have to state such) - so many things have made me absolutely intransigent about this matter.
Perhaps one of the most irritating things I heard on the subject was a man who said "When I don't know whether a woman's 'Miss' or 'Mrs' I always use 'Mrs' because no woman is likely to object if you think she's married when she's not"...
Sometimes I do want a title used (as some PPs have said, in a more formal interaction such as with banks or solicitors or whatever, at least initially) - and that title should not denote whether or not I'm married. It really is no one's business except mine and my partner's. Otherwise, then Firstname Surname is fine; when the relationship moves over into the more relaxed, then Firstname is equally fine.
I've really fought some hard battles for my 'Ms', including walking out on a (temporary) job. I shall always be 'Ms'.
(Oh, and there's always ways past the forms and the idiocies of officialdom - it just takes a bit of trial, error and ingenuity...)