It's simply not possible for everyone to refuse to fight ONLY fighters ranked above them. This is a pretty simple concept, mate. Imagine any opponent that Garry might face - ranked above him, obviously. Now imagine that guy has the same attitude Garry does... how does the fight happen? how does any fight ever happen?
If he wants to become champion he needs to string together wins against names, not necessarily rankings. The rankings will change and/or be ignored in favour of the most marketable matchup. We all know this.
So, Garry's position is dumb for two reasons - 1) refusing to fight anyone with a rank lower than you isn't feasible - if everybody took this attitude, there woud be zero fights happening. 2) Rankings don't matter as much as notoriety and marketability does. Buckley is 100% right to say that a matchup against him is more valuable than against some unknown top-15 fighter because of the name that Buckley has.
So, "deserve" has nothing to do with it. Practically speaking, Garry is wrong and Buckley is right. If Garry is dead-set on quickly attaining the title, he could do no better than to take fights with the biggest names he can arrange, and ignore the rankings.
#14 ranked Dan Henderson fought for the title, and it isn't because every single fighter ranked #1-#13 were all sidelined with injuries.