If a person is inclined to share abhorrent views or post tasteless comments, why not in the same account? Posting that material through another alias won't minimize your anonymity at all.
Furthermore, this is an Internet forum, not a 'hate' site. The intention is for dialogue that would otherwise be prohibited elsewhere because of their volatility. Most users here are highly anonymous and have not given out much of their personal details. Protecting themselves from their own opinions makes no sense when those opinions are endorsed by the forum's Free Speech policy.
Finally, posting through another alias defeats the whole point of this rule, when other members can subconsciously pick up who they actually are. Only well-seasoned trolls can pull off convincing "alter-egos". From what I've gathered, however, many of the folks behind these double/triple accounts can't be bothered to do that.