Also the points and the increased insurance premium for several years? I think at worst, the financial calculus would be a break even but at least he would get justice and not get points on his license.
I would have to look more into the charge, but I feel this is the equivalent to a seat belt ticket in terms of an insurance hit, unless you have several tickets already on your insurance. Obviously everyone's driving history will vary, but I doubt the cost of an attorney alone would make it cost effective.
I also understand it is the principal for the OP, but is that worth risking a $300 ticket turning into 12 months probation, $1000+ with fines/fees, and other conditions? People who fighter charges and lose get hosed.