We tried making the voting age 21 and it did not work. It was not fair to the people who were being drafted in a war they had no say in. Hence the Twenty-Sixth Amendment. Should a draft be limited to people who pay income tax?
As far as limiting voting to income taxpayers, what about all the other issues that effect everyone? For example, what about war? That issue affects every citizen, wether they are an income taxpayer or not, they should be allowed to voice their opinion on it by way of voting.
Also, what about all the other taxes? Income tax is not the only one. There is sales tax, production tax, import tax, capital gains tax, estate tax, death tax, etc. Everyone in this country pays tax one way or another so we all have a right to vote in order to voice our ideas on those taxes.