“Penetration is the woman’s role”?

For millennia, men and women have clung to the archaic attitude that sex is all about establishing and reinforcing boundaries. One of the most rigid stereotypes about sex is that men should always be the penetrators, and any man who gets penetrated is either gay or a "sissy." Dr. Charlie Glickman and Aislinn Emirzian examine some common stereotypes about gender, sexuality, and penetration in
The Ultimate Guide to Prostate Pleasure: Erotic Exploration for Men and Their Partners. Letting go of these preconceived notions can tear down the barriers in your sex life and open you up to a new form of intimacy that's built on mutual exchange instead of give/take. This straightforward excerpt from Chapter 13 (which is titled "Real Men Don't") implicitly asks: What are you afraid of?
“Penetration is the woman’s role”
From Chapter 13: Real Men Don’t

Receiving penetration is sometimes thought of as the woman’s role in sex. And since a big part of being a “real man” means that you don’t do anything womanly, then of course receiving penetration doesn’t fit. Some men fear that if they get penetrated, they are being feminized—turned into a sissy.

Of course, the negative judgment about a man taking on the woman’s role only works if you think there’s something wrong with being a woman. Many men have internalized this judgment without ever considering that is based on the idea that women are inferior and therefore men should not be like them. Ask yourself: do you really believe that women are inferior? What’s so wrong with women that it should be a terrible thing for men to resemble them?

Also, the idea that in sex men have one role and women have another is very restrictive. Men should do all the giving and women should do all the receiving: these roles work fine if your sex life consists only of fucking with the man controlling all the motion. But a lot of people with very satisfying sex lives have roles that are more blurred: for example, sometimes the woman hops on top and controls the motion, or fucks back on him from underneath. Sometimes the woman gives a blow job while the man sits back and receives. Who is playing what role then? It’s not always an either/or.

It’s also worth thinking about how it can still be a woman’s role if a man is doing it. In some ways, it’s similar to how women used to be attacked for wearing pants (i.e., “men’s clothes”). In our view, if a woman is wearing pants, they’re a woman’s clothes. Similarly, if a man gets penetrated, it’s his hot sex!

The belief that only certain people ever enjoy or engage in a particular sexual practice holds a lot of people back from trying something they might enjoy. We’d much rather have people decide what they want to do based on their (and their partner’s) consent, pleasure, and well-being than on someone else’s opinion of what they should do.