They would make him expend energy to defend himself from them, which is something but isn't direct damage. Still, you're right that it's not 'nothing'.
Still, vampires treat things that aren't fire or other things they're specifically weak to... or magic that fucks with regeneration... as being no more dangerous than being punched by someone even without Resilience.
And on the consent point: You are right that in many US states the laws on this matter are actually really vague. In New York State, specifically... well this is from a Reddit post so don't take it too seriously, but it's the best I found on short notice:
Being "incapable of consent" is a little less clear, and is defined as a condition where any of the following apply to the victim (as specified in subsection 3 of NYS Penal Law ยง 130.05):
The individual is less than seventeen years old.
The individual is "mentally disabled".
The individual is "mentally incapacitated".
The individual is "physically helpless".
The individual is incarcerated.
The individual is committed to some kind of medical facility (e.g. a hospital).
In New York, you are considered "mentally disabled" if you have some sort of mental or neural condition which prevents you from realistically judging the consequences of your actions.
You would be considered "mentally incapacitated" if you were under the influence of an intoxicating substance only if you did not serve yourself the substance, although you might be "physically helpless" if you drank enough.
In other words, according to the laws of New York, if you got yourself drunk, but weren't so drunk that you became helpless, you are capable of giving consent, although if someone spikes your drink or puts a date rape drug or something of that nature in it, it is always considered rape.
The actual point at which you would become helpless is something a judge would analyze if you filed a complaint and the local attorney decided they had enough evidence to prosecute.
So you are partially correct in how it works at least here legally. Elsewhere, I don't know, but I've still heard it said that it's considered pretty shitty (if not actually illegal) to have sex with someone who is drunk unless you're about as drunk as they are. I don't know because I don't drink.