I think the groups seem rigid and toxic because they will tend to attract the zealots. Most people will just read an article here and there and mix it in with their own experience and ideas. I think gentle parenting and attachment parenting give food for thought, but I've also seen families who seem to have taken it too far (a family member was into all this, and all their friends from the groups seemed a bit nuts, with a high proportion of kids with behavioural issues, though I don't know if the parenting actually caused or exacerbated the issues, or was in response to them).
Personally, I had one parent who was gentle, respectful but also reasonably firm. My other parent could be affectionate but more on the shouty, short-tempered end of the spectrum. There was certainly no attachment parenting going on in my family, in the sense of extended breastfeeding, co-sleeping etc. We turned out OK. Any difficulties we had, I'd put down to other things.
With my DC, I take inspiration from the best of what my parents did, and sprinkle in a dash of parenting tips from various sources, including things that overlap with gentle or attachment parenting, but I'm certainly not fully subscribed to those philosophies. I don't lose my temper, but that's just my personality, thankfully.
I think it's OK for kids to see you a bit peeved sometimes. I don't mean shouting all the time, but if they cross a line I don't think you have to be sugary-sweet and trot out a "gentle" script. Particularly with younger children, I think they can just get confused by an insincere smile and a lecture on "kind hands" and "it makes mummy sad". I'd rather be straight with them and show them my real reaction (in moderation), so they learn how people react to behaviour. And I think it gives them permission to have honest emotional reactions too, developing emotional intelligence. I don't want to model total repression, or emotional blackmail. I'm sure that's not what gentle parenting is supposed to do either, but it's what I've seen from some families.