Firstly, there should be abundantly more evidence than that is presented to ensure they are alts. And besides, if those alts of his are banned, there's no guarantee that he will not go ahead and create 5 more alts in a day and continue his activities. The most effective means to curb this is to report and possibly ignore if it persists.
OP dropped a link to the thread he created on reputation thread about the owner of that account and his possible alts which other reputable members also were able to draw similarities in writing and posting patterns from possibly the same account. Maybe to clear the doubt as to their claims if the possibility of that account being linked to other accounts, OP would need to present evidence beyond just writing and posting patterns as that is what the forum could consider and look into before taking actions against that account holder and his other army of alts.
If you and uchegod-21 had read what I wrote a few posts above yours, instead of just reading the OP and rushing to reply, you would realize that the main argument for banning him is not that they're alts of a banned user. The main argument is the constant and repetitive violation of rule 1. That's the main argument. The fact that they're alts of a banned user only reinforces that point.
Apart from that, I've reported a few OPs on the Economics section for low value. Let's see how that goes.