Don't care if people want to multibox or macro.
All that matters to me is if they are behaving badly towards other players and affecting basic game play of others. Examples - If a macro goes out of control and the owner doesn't intervene, or the owner doesn't respond to another player asking for a turn farming mobs at a navigation buoy then it would be all right for a GM to kick and warn them.
A whole game of nothing but macros might be bad though.