If that user doesn't have many people blocking them, then this will barely affect the votes. If they have tonnes of blockers, then would indicate that they probably deserved it, and the downvotes would make sense anyway.
It would prevent echo chambers from forming.
If you are on a bigger forum, block a few because you just don't want to see their posts. Or they are bots. Suddenly you have huge problems on small subreddits.
And I don't see a huge benefit to it. People clean up their block list maybe? But for what.
if the sub is small, then 5 blockers might be significant.
I suppose the arguments regarding the bot accounts are valid, as it allows for manipulation. Presumably reddit should be blocking bots, but of course that's wishful thinking.
This would also create a tool to cast target people to oblivion.
The real question is to ask what is the real problem. I understand that an online places can be gritty because of incivilities, but a dogme is much more scarier to me than an online idiot.