At almost sixty and infirm, karate (and also aikido, which can be hard on the knees) can give you significant training injuries. Overtraining for karate and TKD competition for a few years set me up for a lifetime of knee pain. Jiu-jitsu, Brazilian or otherwise, is an excellent alternative. I think that you should constantly strive to avoid any conflict that could leave you injured, facing assault charges, or both. People who get into fights need money for hospital bills, bail and a good lawyer.