There is something to be said for being the kid that never starts a fight but can discern when to finish it.
Bravo for sticking up for your kid.
My kids knew I would be the first to hold them accountable if they screwed up & the first to defend them if they were in the right. I also didn't tolerate lying, they would get a bigger punishment for lying then for what ever else they did. It behooved them to tell the truth. In the same vein, I was one that saw no reason not to say yes to things when possible, & if I said no, they could always come back with new information & we could discuss it further. I have frequently been voted M.O.M. (mean old mom) and proud of it.