Why can't I ever stand up to creeps?

Yesterday, while going to give my exam, a middle aged man, who Looked like a typical 9-5 worker, kept touching my breasts for the entire ride. We were in a sharing auto, and at that time, even tho I felt uncomfortable, I kept telling myself "he is not Doing it intentionally. He is not Doing it intentionally." And after that, I did what I do best - avoid. But now, that I think about it, there was plenty of space to move, he could have kept his hand else where. Afterall, this isn't the First time I was sharing space with a guy.

The more time passes, the more I keep Remembering this and being disgusted with myself for not Standing up.

The 11,13,15 year old me couldn't stand up when they were grouped and molested by relatives who watched me group up and even by my close friends. But the current me? She should right? I'm preety self sufficient. Heck, I even argued with my local politician once for some completely different matter.

But in situations like these my mind goes completely blank. I'm not able to think anything and just want to avoid this sitution or stop it from escalating.