So you won't listen to, say, people convicted of minor drug crimes, or who have otherwise been disenfranchised for any of a wide variety of reasons, some good and some not-so-good?
I think most people who make the "people who don't vote..." argument pretty clearly mean "people who choose not to vote", not "people who are denied the opportunity to vote".
But since it's already been convincingly argued that our "opportunity" to vote just gets us carbon copies of the same policies, isn't that very much like being denied the opportunity to vote in the first place?
No, its not. Your choice might be limited and imperfect -- and if you think that's the case and are bothered by it than you should be engaged in efforts to change the system that creates that problem as well as voting -- but that limited and imperfect choice is not the same thing as being disenfranchised.
As soon as you started using subjective terms like "very much" and "convincingly", yes, it was in matter of opinion territory. But if you ask a question with terms which inherently call for an opinion, you can't (justifiably, at least) complain that the response is in "matter of opinion" territory.
You live in a Democratic country. Is it any surprise that the majority of educated people are committed true-believers in the Democratic process, despite all evidence that it may be broken?
Yup, I just won't listen to them.