While I don't personally dislike multilogging, I can see why someone would make this post.
However, from what I've read, I feel you're bringing up the wrong negative effects that it could/does have.
Sure, being antisocial on 4 of 5 characters isn't the greatest thing, but the negative aspect that I see would be scenarios like:
A player with 65 mining can mine, lets say, 300 coal an hour.
Or, the same player, could make 5 alts to have 1 smithing/fletching/cooking/herblaw but shoot for adequate mining/woodcutting/fishing/etc stats to supply the main account with materials to level the appropriate skills.
In the example above, this would increase the individual players productivity from 300 coal an hour to 300*6 per hour, or 1800 coal per hour (effectively doing 6 hours of work in a single hour)
Obviously the number would be lower, taking into account some misclicks, and times one account will instantly mine the coal while another may take upwards of 7-10 seconds and fall a little behind, but you get my point.
To reiterate though, I don't particularly have a problem with multilogging. I am simply saying, I can understand why someone wouldn't particularly like it from an economic perspective.