Tend to agree. Yes, there are ways of cold setting that are more controlled (and less likely to be cocked to one side or the other) than the OP's method, and any proper cold-setting always requires realignment of the dropouts to do it right - which doesn't seem to be the case here.

However, provided a frame is not heat treated steel (or aluminum - obviously), the amount of strength lost in the steel is minimal - and not much different from a framebuilder re-raking a fork blade or chainstay for tire clearance. You'll never feel it in the saddle, and it's not going to crack open 20 years from now from this minor adjustment.

-Kurt