There was nothing inflammatory in your original question; the respondent has an obvious axe to grind. Anyone associated with a Philadelphia charter school MUST know the public perception of charter schools; namely, that they are a financial scam using taxpayer dollars. If you know this, you don't react as the respondent did.
My reading on charter schools in Philadelphia is that they deliver less results than the standard public school but at a cost 5 to 6 times greater on a per student basis. That is the real issue that educators have with charters; cost effectiveness and to date, they don't seem to have proven they are.