Too soft?

My maternal grandfather (God rest him) was a wise old Irishman from Co Westmeath Eire. His (& mine) claim to fame was that his brother John, was a celebrated author & playwright whose pen name was Brinsley MacNamara. Anyway enough of that. My point here is this: He had a saying that he used when he felt that someone was being taken advantage of & it was..."(so & so) would stand for the three card trick".
You know, I think that that applies to me.
I'm too soft, a mug I let people especially family walk over me. They get away with blue murder, they & others are all too ready to give their opinion on what I'm wearing, reading my choice of music etc etc. Where as I never pass any opinion on any of those topics to others. Maybe I was brought up to well mannered, or I'm shy, I don't know.
What comes to mind is my sister in law, who. upon reflection as a paranoid persecutary personality (but is that justification?) openly mocked & criticised a book I was reading to my face in front of others. (the book was one of a trilogy about Julius Caesar & his relationship with Marcus Brutus, the Roman Civil War etc. A lot of the story was poetic licence granted, but I enjoyed them greatly.) I stood & tried vainly to explain my reasons why I liked the book & so forth, but these also were put down. Now I think I should have told her-"Look ******, stop being such an ill mannered arrogant snob & fuck off.
In fact I think there are lots of people who rile me & I should tell them exactly what I think,maybe tell them to shut the fuck up or to fuck off.
I'm tired of being taken for a mug, a fool and..."standing for the three card trick" So.......