Why do people who insult you or put you down accuse you of being 'stiff' around people?

Like they may have been so for years and so you distance yourself and when you are in their company you are reserved and speak when spoken to and you're obviously not going to be open and friendly and uninihibited in their presence. They have taught you not to be because they have no respect. I mean ofc you're going to be 'stiff' around people that mess with you or insult you. WTF are they on about?