It seems your fundamental break with libertarians is grounding your arguments in consequentialism rather than morality. I basically agree with everything you say especially the part about relying on experiment. My only quibble is the redistribution part. It seems that you agree with me that markets work better in many instances even ones that say a moderate Republican might reject such as environmental policy or organ donation. However, you seem to think that this is not the case for charity. i.e. that politically decided redistribution is more effective than private redistribution (charity). Perhaps, you are aware of some experiments that I am not.