The RAF is a supporting arm for Defence, the RN and Army the supported arms.
He's talking garbage, don't rise to it.
Some of the RAF's output does indeed support the other arms (JHC, AT etc), but some is an end in itself in pursuit of the overall national/ war goals (AD for eg).
It could be argued that CAS takes out the enemy frontline & the army support the RAF by occupying the territory that has just been cleared....
It's all a matter of perspective.