The difference between ''Give me your spot or I will KOS you'' or ''Give me pet tickets or I will KOS you'' is, in my eyes, nearly the same thing. A better spot gives you more pet tickets, so taking it from someone is effectively reducing their pet ticket income (amongst other things that drop). In both cases the punishment, for not doing what is asked, is the same thing which is not being able to xp/farm since you'll get killed.
The only difference between those two things is if it's direct (trade item for favour x) or indirect blackmail (gtfo or else), both resulting in the same thing. The powerful person ending up with better things/more things while the weaker gets less. One is completely legal whilst the other is a bannable offense, doesn't seem right to me.
I like your walmart example but it's not the same. Example one is simple competition in which a giantic company kills off all smaller competition simply by being able to be cheaper due to their size and bulk buying/selling. This includes no blackmail and is just the way economics work. The second one being plain blackmail for ''protection''. Both extortion for a spot or extortion for pet tickets is in fact blackmail with the only difference being the reward.