> The basic definition of theft is taking something from someone without their consent.

I can go with that.

> The government has a monopoly on violence

Yes, but not unconstrained or arbitrary violence (mostly, in democracies at any rate). Property rights depend on them being enforced. So while the absence of a government might mean you didn't get taxed, good luck holding on to any of your property without laws, courts and police.

> And we're better off with government than without it.

I think we basically agree :)