This is one that has always bothered me.
I was given frequent, unnecessary enemas as a child. Not that I objected, I would do whatever I could to get them.
But if I got an erection I was told that was dirty or nasty. When I got older I was told if I was caught playing with my penis my mother would take a match to it and burn it.
I was told my penis was not to be played with, so at first had terrible guilt about it. What got me over it was a male friend who demonstrated how good it was by masturbating with me watching until he came. When I tried without success he took over and I had my first orgasm.
The same fellow taught a bunch of us to masturbate. I know what you might think, but he is happily married with a couple of kids.
My next encounter was with another male, and we tried anal intercourse... he got too much pain, but i loved when he pegged me.
So more assumptions, but maybe not what you expect. I like girls, and as soon as I had one I could play with, I chose to play with her, and so did my friend.
And now, 60 plus years later, I still prefer women, but have had a couple of enjoyable threesomes along the way.