Should the US have a flat income tax rate?

Always a topic of lively discussions...especially approaching election periods. The flat rate really isn't much of a solution to anything...in fact right now we have a 3 rate system on earnings ( a slightly different rate on caoital gains or dividends)...The 3 rates are actually 2, since one of those rate tiers is a small 5% bump within the higher of the rates (applicable for only certain earning amounts and then goes away). I really don't think making one rate would simplify this much...nor is it terribly complex now. However, more than the rate issue is the confusion caused by determination of what is taxable income...with different definitions of different types of income, many, many different exclusions and deductions (like mortgage interest), making it so 2 people with the exact same job and wage could have an entirely different amount of taxable income to apply the same rate too (based on different number of children, dependents, marital status, interest rate and amount of mortgage, medical expenses etc.,) makes things very unclear. And perhaps, unfair. (Why should someone with the same wage as another, but having more children - presumably all using more services than the one with none - be able to pay less tax?)