I don't think rape was considered a concept in Poldark's time
Either by men or women.
I just finished reading "Warleggan" and there was a scene where Ross is in Demelza's bedroom and he thinks about how he could force himself on her and how she would only put up a token resistance, but ultimately he decides not to do that.
This is the passage: He knew he could take her if he wanted, and her resistance would only be token; yet the token was there, and while it existed the reconciliation would be ashes.
And when I read that, I'm commenting, "Yeah, just like Elizabeth." And it's absolutely the same mentality that O'Neil has when Demelza is telling him she doesn't want to do this and he starts trying to force himself on her. It takes her biting his hand to get him to finally back-off and basically blame her for not putting out. Then you've got Sir Hugh and Sir John outside her door tossing a coin to see which one will get the shot to rape her, since they feel she invited them up there and wants it. It was a good thing she climbed out the window and escaped all these guys. But the rub is afterwards Demelza doesn't even seem to blame O'Neil for his behavior towards her.
It makes Ross no different from O'Neil, Sir Hugh and Sir John. They all seem to share the same mentality. Because of how a woman acted towards them [Elizabeth telling Ross she realized she loved him instead of Francis, and Demelza acting flirty towards these men] even if they try to fight them and push them away when they want to have sex it's just a token resistance.
But at that point in history men could do stuff like that and it wasn't considered rape to them or the women, apparently. It wasn't that long ago marital rape wasn't even recognized as being raped.