Ah so its not a single piece arm - single piece arm is the vertical and horizontal that the cable then goes through all as one (giant L if you remove it).
I assume you're talking about this?
A later "low lift" arm (less travel and less effort iirc)
Must admit every box I've ever had pass me by has used the earlier arm, but if you can't wiggle it out then yer i'd guess pop the bush out to give you a bit of angle to work with. Can't see any other way of doing it without putting an angle grinder to it