Karate isn't about using force. Karate also does self-defending. I trained karate
But remember we not talking "fighting" someone, this is about neutralizing
someone in small confined quarters;
a bathroom, small walkway, between seats, etc, - places where you only have inches to move. Will karate be appropriate for that?
You do not want to get into a "combat" situation with someone (leading to lawsuits) - you want to "limit" their movements.
Styles like wing chun, FMA grappling, Aikido, Krav Maga and the likes are more suited for that.
In addition to Wing Chun, I also studied Tae kwon do and also did some Muay Thai so I know a little about the subject and the difference. Right now I am into tai chi chuan and about to take up yoga - I find these two "arts" are great for relaxation & exercising.