Actually, a "business district" is defined under section 235 of the (California) State code. And section 22102 also of the California Vehicle code prohibits a u-turn in a business district. A u-turn is also prohibited in a residence district so unless this was out in the boonies, and regardless of how you describe it, that entire combination you did there was in violation of at minimum, one law.
A u-turn is defined under CVC 665.5 as
665.5 A “U-turn” is the turning of a vehicle upon a highway so as to proceed in the opposite direction whether accomplished by one continuous movement or not.
That is a pretty broad definition where the "one continuous movement" means there was no three point turn and aside from the stop at the stop sign, it sounds as if it was all done in one movement. That still won't make much of a difference.
I think it will boil down to a subjective argument depending on how far into the other street you drove. You're free to make the argument that you were wrongfully cited but in the chance that it might not fly with the judge, there is no guarantee that you will be allowed the traffic school option and so it certainly includes some risk in fighting it.
Two more points just to help put things in proper perspective... (1) The possibility that other cars make the same turn does not make it right or legal and a video is not likely to help your case any. And (2) your clean driving record really means very little since it does not immunize you from committing a violation nor does it imply that you've never violated the law. Only that you have not been caught. Fact is, we all start out with a clean driving record. Some go through a lifetime without any tickets or accidents, others develop as knack for violation points.

Quoting
adjusterjack
California is broke and its judges seek revenue enhancement
What is "revenue enhancement" and are you suggesting that judges will wrongfully convict a defendant in an attempt to help the state get out of debt?
You say that so matter of factly, as if it is a forgone conclusion that regardless of what the cop was forced to admit, the end result is a guilty verdict...., because this judge will seek revenue enhancement, and yet you also suggested that the OP should put the cop on the stand to get him to admit to whatever.... What would be the point of that exercise?