Earlier quoted context omitted.
You're entirely right, government spending does not harm economic growth.
I can't tell if you're being sarcastic, but I think it's important to note that if you make the reductio ad absurdum argument that a tax rate of 100% has strongly negative effects, sure I'll go with that, but if there's a claim that what we have right now is either too much or too little, then there needs to be some sort of evidence to support that claim.
There's another pole to reductio towards, though -- governmental spending increases without commensurate increases in taxation. I don't know enough macro to know what the resulting inflation would look like, what would happen to interest rates or exports or quality of life etc etc... No doubt mainstream economists would be aghast at the thought (it isn't a mainstream idea, after all -- our recent stimulus has been monetary, not fiscal, and it's only meant to be a short-term thing) so it's probably not such a crash hot idea either.