He did pay $750 in taxes that year during filing. Why? Because he was short $750 after prepaying the estimate taxes prior to filing during the tax year, like everyone else who doesn't live on paycheck but owns their own businesses, self-employed, or stock traders. It is a common sense things among most people who are self-employed.
Which begs the question who are these Democrats? A bunch of paycheck to paycheck (assuming they have a job) company drones, min wage workers, etc... who never had to file anything other than the EZ form.