Exactly. This 'flat' tax isn't even flat. A real 'flat' tax would be $2,000 per year regardless of income. This tax is already directly proportional to your income.
Every person we exempt from taxes is a person who will almost always vote for higher taxes for the rest of us.
ETA: I'm the only earner in my family, we would benefit HUGELY from exempting the first $50,000 and I'm still against it.
Last time I suggested that the truly "fair" but impractical tax would be, everyone would pay the same amount, not the same rate; I got booed. I admitted it's not practical. If we divided our current spending by the number of earners, each person would have to pay ~$20K/year. Obviously not practical.
Okay, so even though paying the same rate is not as "fair" as paying the same amount, the most practical fair tax IS a flat percentage of income. I'm okay with that. But the socialists boo that idea because it doesn't punish success.