Say P is "Pay taxes" and M is "deserve to vote". The original claim is: If P then M. What I am pointing out is that the original poster thinks M without P. I

Say P is "Pay taxes" and M is "deserve to vote". The original claim is: If P then M. What I am pointing out is that the original poster thinks M without P. In other words, the original poster thinks that you can deserve to vote even without paying taxes. If that's true, then "I pay taxes therefore I deserve to vote" isn't meaningful because you apparently deserve to vote whether or not you pay taxes. Another way of looking at it is, suppose the original comment said "I am tall, therefore I deserve to vote." If someone replied "Do you think short people deserve to vote?" What this line of questioning is trying to pin down is, what is it, exactly, that entitles people to vote. If short or tall people can vote then it seems that height is not really related to the right to vote. Analogously, if tax payers and non-payers alike can vote, then it seems you think paying taxes is unrelated to the right to vote. To return to symbolic logic - "If P then M" and "If not P then M" means that P isn't really related to M. P says nothing about whether or not M. That's the point I was trying to make by asking about the inverse.