No, I take offense to the notion that American citizens who don't pay taxes should have no say in their government.
But he didn't say that. There is a difference between saying that non-tax-payers will vote for the wrong things, and saying that they shouldn't have the vote at all.
His point seems to simply be that, if half the voters aren't paying taxes, they will vote for politicians and policies that take more and more money from the tax-payers, and give it to the non-tax-payers.
And he seems more troubled by the contracting tax-base, than by the extent of the suffrage.
In counterpoint, it might be suggested that the lower brackets of income are less likely to vote. If this be the case, much more than fifty percent would need to be tax-free, before they would form a majority of actual voters.