Because a lot of people on the right don't like what is in the "for the left" column and a lot of people on the left don't like what is in the "for the right" column.
Right. But I'd also add this: it could be a matter of degrees as well. If he's simultaneously "extreme left" on some issues and "extreme right" on others, the stuff from the other side doesn't become palatable. That's generally the problem with libertarians. They generally seem more ideological and inflexible than either cons or libs.