Moomin
I am dreadfully sorry you feel judged. I assure you, the bfers are as well, inc by HVs. I can tell you lots of ghastly stories. Some mine, some other people's.
nd it suddenly goes from a few nasty people, who would probably be nasty whether they had a baby or not,
Precisely! Nail. On. Head.
Those people aren't nasty about ff because they hate ff. They are nasty about it, because they ended up bf, and they can only feel secure in their own choices if they rubbish all other possibilities, so that their own becomes a default. They're like this with everything, not just infant feeding. They feel you ff'ing as an attack. Unfortunately for me, in case you haven't realised, I know some of these people well. Not by choice. She's my mother. 
The moment you made them seriously consider the possibility that ff is not only an acceptable choice, but sometimes the best choice for a family, they wouldn't be able to leave it there. They'd spend the rest of their lives panicking that maybe formula was better and they'd failed their child by breast-feeding.
There are lots of things to worry about. My children didn't get colostrum, for example. I cried when I saw a poster about colostrum for the first time, post-birth. And then, I thought, "knowing the information on this poster, is there anything I could have done differently?" The answer was no. Then i asked, "were the decisions I made all for the best of -my- family? If they weren't, would it be the poster's fault or the fault of the hospital?" Answer, respectively, was yes and the hospital. Then I asked myself, "Why am I crying?" Answer: because I feel guilty.
Then I went over that line of questioning all over again, and suddenly the guilt fucked off, as I realised that I thought I'd made the right decisions, and I was just feeling guilty for not being in the right position to give colostrum.
After that, I didn't care that I'd supplemented with formula, either, because it's exactly the same. If I went back, I would still use that formula, and I still wouldn't feel guilty.
Mind you, my mother doesn't know I used any formula, and they're school age now, but that's not because I feel guilty or scared. I just can't be doing with the hassle of her anti-ff tirades!