I'm not sure why one bad apple would ruin it for everyone. I've let people stay at my house while they're traveling or in between places or whatever. The vast majority of them are good house guests. Some are not. I don't generalize that the ones who are not means there's no such thing as a good house guest. I'm a good house guest. For the people who weren't good house guests, I'd consider not inviting them again. For the people who were exceptionally bad mooches, I'd confront them about contributing. In the past when I've owned cars, I've been happy to offer rides to anyone who needs one. If someone was abusing that privilege, I'd say I couldn't offer them a ride. If someone burnt a tank of gas taking advantage of me, I'd ask them to pitch in for gas money.
I let people use my Wifi. If someone abused it by P2Ping like crazy or deciding to cancel their internet service so they could mooch off mine, I'd block them and probably not consider allowing that specific person to do it again. I don't think that would change how I treat others.
Like, I live in a 1+ million metro area city. There's the typical issues. I live somewhat near a shelter and next to a public housing building that has pretty much serial low level crime or disturbance issues. I lock my door. I'm not an idiot. But I still give leftovers to my neighbors, invite them in when we're having people over, try to hold the door for them, say hi, let them know if their laundry is done in the laundry room (and I'm very grateful the few times I've forgot mine there and my neighbors have let me know or even better brought it to my apartment for me). I'm not sure why anyone would internalize this sort of me-against-the-world narrative where everyone is just waiting to pull one over on you.
I think being taken advantage of teaches you to temper your judgment and to understand how to protect yourself from abuse, but I think it's bad if the way you decide to protect yourself is just to totally turtle away from the world.
oh man, thatll show him!