Correct me if I'm wrong, but isn't NI specifically for pensions, unemployment and disability payments anyway? You know, insurance policy for when you need it? (I've been wondering if there would be the same legal ramification doodahs of the government cutting welfare payments as there would be to any other insurance company that defaulted on contractual/statutory payouts but probably not!).
As for the rest of it - I'm more than happy to pay NI and taxes to get the benefit of this insurance if I ever need it, the NHS, roads, police, binmen and -women etc. I don't want my taxes to be cut. But I wouldn't mind the option to refuse to pay NI if my insurance policy is with a deadbeat provider.
Collectively, we can afford all these services together if we all pay according to ability. Individually, if tax cuts result in them being taken away, we can't.