But, you know you are sinning when you gossiping.
Homosexuals don’t think what they are doing is a sin, big difference.
A lot of people do not know they are winning when they are gossiping. And religious people know they are sinning when they have any form of extramarital sex. So your point doesn’t really make sense.
My point is that everyone sins. Usually we allow Gd to sort it out and we don’t worry about each other’s sins. But if the sin is yucky to you, you will dwell on the other person’s sin, even if it’s not such a horrible sin.