There are 2 components to the equation. Income and tax rate. Our side believes in increasing the revenue by clearing the path for people to earn more. The other side would rather increase the rate to increase revenue and also use the rate to punish those who earn "too much". We must understand that the curve is dynamic, not static. The lower the tax rate, the more income can be produced by tax payers. I support the philosophy that takes the rate as close to 0% as it can go. Not the other direction.
But Laffer curve doesn't show it that way. To follow your description, it would have had only the second part of the X-axis, but starting from 0% tax rate. Don't get me wrong, I understand what you're saying, and agree with it. But, having 0% tax rate is just not supported by the curve you showed.