I'm all for the office of the tribunes, but if their restoration was the principle over which Caesar fought (rather than a mere pretext, why did Caesar himself nullify their office once he attained power? Why did he hire armed thugs to keep the tribunes out of the forum while passing Pompey's land bills? Was Cato himself not serving as tribune at the time Caesar had him arrested? What kind of adherence to principle is that???
There was only one kind of tribune that was sacred to Caesar, and it was the Tribune of the Caesarians not the Tribune of the People.
I agree in some context, but he still used the affronts against the tribune as a 'reason' for his march on Rome. Its a very key factor in convincing his men to march with him. We've argued the 'legality and personal motivations' many times, so I personally have no reason to rehash and will leave that part to others who feel so inclined.
I am only countering your claim that Caesar himself said that his own dignity is his only reason for marching on Rome. Whether we agree with him or not, he does very much make the claim that the affronts against Antonius were important.