Should I be offended or laugh?

[Mixagon_imp]

Here in the UK hardly any rider waves, the nod of the head is more the normal or the lifting of the foot for sports bike riders.
I nod at most 2 wheelers even scooters but on a busy day it can cause neck pain so if there's a few bikes coming towards me I only nod at the first and last.
I have noticed this year a few don't nod for some reason.