If that's all you have, it's better than nothing. But rule #1 . . don't take a stone to a tank fight.
There are those who will argue that a 22 "will do the job" . . perhaps it will but in how many cases. And, you may be "proficient" . . but how proficient are you when put in to an extremely stressful situation where you have adrenlian pumping though your system and it is "kill or be killed"?
In my work experience in ambulance and in fire rescue, I saw more than my share of gunshot wounds . . . both fatal and non-fatal. Add a perp that's tanked up on drugs and it's a whole different story than someone whoo isn't.
A person can argue about a "well placed shot" and how good of a shot they are . . . in the end, all that is just "hoopla" unless you can carry it out under stressful situations. And if you have never had the experience of being shot at . . and I have . . . I can guarantee you that you have NO idea of how you will react or even if you can keep your wits about you. All of those things are important factors to consider when choosing a handgun/caliber to carry as well as practice, practice and then more practice.
If a person wants to carry a 22 and feels confident in it . . then it is their personal decision and far be it for me criticize or tell them they should not . . . . but before spending money on a 22 . . . please consider all of the factors that are involved. For myself, when I carry, I want a cartridge that I know is going to have some put down power to it to put a quick stop to further threat or violence. And, I would much rather carry one that will do that job . . . and never need it . . . than to carry a caliber that is "iffy" at best and need it to do a job it might not do.