By all means, this fear isn't the entire basis behind homophobia -- but it's a side of it I hadn't thought of before. The comic that she posted is based loosely on a series of articles by Andrew Sullivan, including this tale:
You struck a nerve with this one [article], as I was just discussing this very thing a few weeks ago with a group of high-school freshmen in my English class. We were discussing homosexuality because of an allusion to it in the book we were reading, and several boys made comments such as, "That's disgusting." We got into the debate and eventually a boy admitted that he was terrified/disgusted when he was once sharing a taxi and the other male passenger made a pass at him.
The lightbulb went off. "Oh," I said. "I get it. See, you are afraid, because for the first time in your life you have found yourself a victim of unwanted sexual advances by someone who has the physical ability to use force against you." The boy nodded and shuddered visibly.
"But," I continued. "As a woman, you learn to live with that from the time you are fourteen, and it never stops. We live with that fear every day of our lives. Every man walking through the parking garage the same time you are is either just a harmless stranger or a potential rapist. Every time."
The girls in the room nodded, agreeing. The boys seemed genuinely shocked.
"So think about that the next time you hit on a girl. Maybe, like you in the taxi, she doesn't actually want you to."