As a functioning human adult, "wouldn't" is the correct word here. It may seem like a small matter, but it's not: saying "couldn't" is a very popular way to represent the idea that men aren't responsible for behavior that others find unacceptable, especially when it's towards women. Please take more care around your phrasing in the future.
> apart from the fact that he touched the hair of his coworker
"apart from" trivializes and sets aside the most important thing we know about Dick: that he touches women without their consent and refuses to honor their requests to stop. There is no "apart from" that weakens, mitigates, or excuses this.
> just to check if the situation can be transformed into harmless/no consequence and they can get out without having to admit wrongdoing
Men who behave in this way are fully expecting other men to let them get away with it. They are right, statistically speaking.
Men, don't silently let them get away with it. It may feel uncomfortable to try to hold a man accountable for their actions. Bad men thrive on how reliably that discomfort makes other men stay silent. They're depending on you being too socially weak and inept to overcome that. I know it can be difficult, and you won't succeed every time, but it's important that you try every time all the same. Best of luck.