Well I can't speak for "leftists", but I happen to think that you should be able to do, think, and say whatever you want - as long as you aren't hurting anybody.
I'm not sure you know what the difference is between a fact and an opinion. okay there is a lot to unpack there so I'll just start with your first point.
The laws "rules" of Human conduct must be compatible with the bio, psycho, and social nature of man.
Must they? Is that a fact, or is it something you heard somewhere and happen to believe. What is the Biological, Psychological, and social nature of man? Are those things you are an expert in? Who sets the perimeters? What is the data on those perimeters? Is it across the board, or are their variants?