In response to your title BeetleBugBaby YABU. Some laws are stupid, incorrect and a person should always break laws that are inherently wrong (no blacks on this section of the bus, for example).
On the other hand, in reference to the 'meat' of your example, YANBU. Breaking the speed limit is one thing, driving and texting is dangerous, seriously dangerous for not just the driver but passengers and other road users and I have no time for people who are so blaze with common sense and safety.
Speeding CAN be judged, so that risk is lesser (I've broken the limit on long straight quiet roads at times) but texting whilst driving is always something only an utter dickhead does.
My DH works objectively in the area of traffic policing (ie he's not a cop) and I have lost count of the amount of times he tells me about the day's fatal RTA where one of the drivers was texting, so much so that I think it's THE killer at present, obviously I only have anecdotal evidence to go on and that's worth nowt.
I do know that for Traffic Police it is an absolute pet hate amongst most of them, for good reason (they have to mop up the mess) and it's unnecessary, and involves injury or death to people other than the prat breaking the law. The same could be said of speeding in some contexts but not all.