I read that as (paraphrasing), liberals can donate all the money they want (in addition to their taxes) to the government for the government programs they support. He then leaves it open as to how many do but I guess he thinks it is somewhere between 0 (zero) and nil.   I don't think he was introducing non-profits/charities.  Personally, I seriously doubt that Steve thinks liberals don't donate money to non-governmental programs they support.