This is absolutely about aggression, even if it is subconscious. The last unsolicited dick pic I got made me feel assaulted and I do believe that was the intent. I no longer have a Fetlife account because of too many guys who think that any woman who is confident in her sexuality is open to sex or sexual conversation with absolutely anyone. I had a young guy “offer” to let me watch him masterbate and when I declined, he got really rude. Too many men still believe that women exist for the sole purpose of their entertainment and pleasure.
Back when I did do dating sites (not for some time) I would not consider the profile of any guy who had a picture of his dick as his profile picture. It told me all that I needed to know about how we were not a good fit for each other.