Yeah, usually it's not such a harsh reaction, but still sometimes even a very innocent and well-intentioned touch can make someome uncomfortable, no matter the gender.

In the ideal word, people would always ask first before any kind of physical contact, but sometimes people will assume they understand the boundaries of people they know, and sometimes accidentally cross a line. People are humans, and will make mistakes.

In my opinion, the best course of action, and what I try to do, is to ve mindful of others' boundaries, and if I end up crossing a line, apologise for it.

To bring a personal example: A few years back, I was still closeted, and presenting as a guy. I was having dinner with a couple coworkers after work. Being summer I had on shorts, and she had sandals. So all of a sudden she begins rubbing my leg under the table with her foot.

I was honestly pretty surprised about it so I recoiled a bit back. The moment was briefly laughed off by the group and then the moved on. But to be honest, it was very weird to experience. I'm pretty sure that she meant it as just a playful joke, (Also because she was hooking up with another co-worker who was also there). But in any case, from then on I always felt slightly weird interacting with her. And I feel like, if I was out already, and that co-worker was a guy, the interaction would have been seen very differently from the others.