IME men in general are vvv cautious about their female partners, sisters, daughters etc. When it comes to men (and boys when daughter is older) just generally.
Their feelings and judgement of risk around this imo comes from a totally different place to the feelings and judgement the risk posed by men (boys) by women (and girls).
The DH has general discomfort. I would ask what exactly are you concerned about? The walk? Changing? Something you heard about this bloke? Etc.
When it comes to being all too ingrained to pretty much constantly keep male risk radar on. Noticing, assessing. Relaxing. Going into wary mode. Going elsewhere if think hmmm nah.
Women do it generally as second nature since girls. Often informed by experience sadly.
Obviously not infallible but without it we have no idea how much worse it would be. I bet a lot.
OTOH.
Male risk assessment of risk men to girls/ women. Applies usually to those they are related to, care about, are good friends with etc.
It's not IME individual risk assessment. It's a much more general worry about men (boys) full stop.
Its usually focussed on women/ girls they care about,. In this case DD. Chances are he'd be more relaxed with a son in there circs. Even though obv boys and girls are preyed on by child molesters.
Given that, realistically. Whose risk assessment is likely to be more considered, realistic?
Esp given the OH vague reason, generally uncomfortable.