I was hoping someone would say that before I did.
When I hear the term "Grow up", it's usually used as an exclamatory emoting a certain situational exasperation. I certainly don't relate maturity to age. If that were true, the whole phrase would just be ordering us all to go through puberty again. Once was enough, thank you.
Sure, taken by itself that sounds rather arrogant, but it fit nicely into the point he was making. You appear to have associated the lowering as bad. I, as a representative of the five-foot-short community, appreciate any and all who would like to lower themselves to my level. Low is just a different perspective. The connotation that he was 'being purposefully dumb' (or something similar), is entirely based on interpretation. I suppose this entire side-bar would have been averted had Graeme said 'modified', instead of 'lowered'. But then I might get the impression that low is somehow inferior to high. We wouldn't want THAT would we?
-db-