As per the answer to this question, as linked by SSD in this answer, we know that the malus on downvoting was placed to avoid downvotes related to irrational dislike (of certain topics, answers, or people).
I have seen an answer to a meta question (can't find it) that the system needs to be robust enough to power through irrational votes, as there's no real way to avoid irrational votes without exercising control over voting.
Downvotes can 'grey out' an answer, and a quick rush of downvotes can result in an answer being deleted or not-read by most viewers, thus destroying a good answer. But a rush of upvotes can result in an answer being accepted, and other good answers not being read, to an almost similar extent
So, since both irrational upvoting and irrational downvoting can both harm the quality of answers;
a) why is the philosophy of relying on good votes to outweigh irrational votes not applied to downvoting
b) why is upvoting not limited in some fashion to discourage irrational upvoting in the same way downvoting is
c) Why is the emotional investment in good answers (enough to downvote the bad ones at a personal cost) assumed to be higher than the emotional investment in irritation, dislike, or other irrational viewpoints that result in irrational downvotes?