I think the OP was reacting defensively as she was torn apart. This is how I see it.
I don't think she was tarring all men with the same brush at all. She made the point in her first post that she did not know the father. She didn't know his name or anything about him.
Same when she went to collect her dd. She had made arrangements for this friend to come round to hers, she made those plans with the mother, then the father (who she doesn't know) turns up and says that he wants her dd to play at theirs instead. When she turns up to collect her dd, they have been playing dressing up and her dd doesn't have her trousers on.
Now we can all get super paranoid about that but to be fair we all have parenting boundaries. When my kids were younger I would not have felt comfortable with them getting undressed at a friend's house either. It may be different if I had known the parents but if it was first time round at a friend's house with adults I didn't know then I would also be worried.
As a mother I would also discourage visiting young children to get undressed at my house. I remember a party I had for my ds when he was 6. These little horrors all came into the house and one little lad was running around with his trousers round his ankles showing everyone his bum and willy. My dh actually told him that if he didn't pull his trousers up we'd call his parents.
Kids will be kids though! But I was very aware that the parents didn't know us very well and so I really didn't want their kids getting undressed at ours. And that's with me there. I would also not let dh supervise young kids who he didn't know alone. Not because I don't trust dh but it's not fair on the child to leave them with an adult they barely know.
So I don't think the OP is being unreasonable. But some of you have different boundaries and that's fine.
I think the OP is quite protective of her first child and I'm certainly not going to berate her for that. She never, at any point, said that her fears were based purely on the fact that it was a man. Never. She made it quite clear that she didn't know him and that, I think, was her main point. This was the mother's partner who she didn't know.