I'm afraid you have just been misled as to Justin's intentions. Justin has zero interest in debates about upvotes and downvotes.
If you've listened to any of the recent town halls he has participated in, you will quickly find that he has realized he has stepped into a hornet's nest here at Steem, and he's now just looking for a way to get out, without losing any more money than he can in the process.
He's not calling for an end to downvotes (that's a separate group on the site), he wants to change the powerdown delay down to 1 day so that he can make the steemit development stake liquid and then dump it on exchanges to try to recover the money he paid to Ned. If this is allowed to happen, all holders of Steem just lose from it, including you.
idgaf. steem is trash
If you don't care, why did you bother to vote then?