When you meet a person who Can’t Do Better, your first instinct is correct. They are as cold and evil as you feel. They are liars, scammers, tricksters, and will use you, if you give them the chance.
People who Can’t Do Better will treat you like an unflushed toilet until they have a use for you. It could be as simple as getting you to take their side in a discussion or needing you to do them a favour.
They will put up a decent front to make you feel that perhaps you misjudged them.
What you need to do, to maintain your sanity and balance, is to push a ‘stick’ into their cage. As they only talk to you when they want to, as they ‘control’ and you have no ‘right’ to talk to them, as soon as they seem to be angling for a ‘beg’ approach them with some blather and you will get their sharp rejection.
This means that they can not ask you for anything.
You need never to let your guard down. Never feel sorry for them, never create excuses for them, maintain your contempt.