I think that might be it. Fellas always try to talk me out of a 22 whenever I look at one. What good are bigger bullets when I can't manage the heavier gun well enough to aim? I could just work on getting more shots off with a lighter gun.
A .22 would be great for you to learn with. It will help acclimate you to shooting, anticipating the report and recoil (such as it is with a .22) and hitting the target.
That said; while I won't go suggesting, as one did, a .357 shooting .38's, you still need to consider putting a little more energy and mass on the target than a .22 can provide. Sure, with the right shot - a head shot - a .22 is quite deadly but getting that shot, which is a small target in a fast moving, sudden situation may be difficult. And hitting other non critical body parts, especially if we're talking about a 200+lb bubba, might just do more to *iss the guy off than stop him. And if he's in a drug rage, he may not even feel them.
So a .32 or .380 may be in order given your requirements.
Most of all, find an NRA certified instructor. Check nra.org for one in your area. Talk to him. See if there is an indoor (or outdoor if weather permits) range that has arms for rent. Start with a .22 and learn to shoot. Then after discussions with your instructor, find something a little bigger. Try it out. Find one that works for YOU. After all that, then buy.
Good luck and stay safe.
Oh, and what ever you end up buying, buy "Quality". In such an instrument, there is no substitute for quality.