Why do men always mistake friendliness as flirting?

Feel like I need to vent here because I'm so angry and betrayed.

I am 30 years old, a lesbian, and a friendly person. I mention the latter because it often gets me into trouble with men. I am nice to everyone and can make pleasant conversation. I can relate to anyone and make people feel at ease. I ask a lot of questions when I talk to people. People generally like me. The problem is that straight men, so often, almost a majority of the time, misinterpret my kindness for some kind of sexual interest in them. And then I find myself in deeply uncomfortable situations.

I'm currently visiting a small town on a month-long work trip. I befriended a local old widowed man (85). He was nice, told interesting stories, and taught me about the history of the town. He offered to drive me to see some local interesting sights, which I took him up on, because I don't have a car here. He invited me for dinner and I met his son. It was nice. He told me about his grandchildren. He knew I was engaged and have a partner. There was no indication this guy saw me as anything other than a friend until I went over a couple nights ago, ostensibly to watch a hockey game, and he came on to me in such a creepy and inappropriate way.

In the moment, I was completely stunned, because the man is fucking 85. What did he think was going to happen? He was making 'jokes' about me going to bed with him, he kept trying to kiss me despite me repeatedly saying no, he sat too close to me and kept touching me despite me curling into a ball at the end of the couch to try to avoid him. There were a number of other inappropriate things. I felt afraid to leave. I froze, and I was afraid to fight him because the thought in the back of my mind was "what if he has a gun? What if he could hurt me?" I can fight an 85 year old man (I don't want to) but I can't fight a gun.

I managed to get out of there and I was polite the whole time because I didn't want to piss him off - I don't want to enrage a man in his own house and see what kind of situation that puts me in. The day after the next, he came to my door after I'd ignored his calls and blocked his number. I told him he had been inappropriate, that he'd violated my trust, and that I never want to see him again. He looked at me like a wounded animal, like I'd insulted him. He genuinely thought he had done nothing wrong, apologised, and was then confused as to why I didn't accept his apology. I just told him to get out of my sight.

I am still seething with anger over this, not just because of this particular man, but because this is not an isolated incident. I like to make friends with people, and half of all people are men, so naturally I have made many male friends. But more than half the time, they don't understand that all I want is to be friends. They think they are going to be the 'special' one that changes my mind about being a lesbian. They always think we have some special connection. They can't just be normal. They can't just see me as an equal human being, see my perspective, or see me as anything other than a sexual object, apparently.

I am mad at myself for not being a better judge of character and mad that I put myself in a dangerous situation. But on the flip side, isn't a sad existence to forego friendships with men? To not trust men? To close yourself off to relationships with half of the population? How do we navigate this as women? How can I not become jaded and embittered? I'm so pissed I just want to go live on a lesbian island and never talk to a guy ever again.