Not to defend Greece but to explain it:
When exchange rates between countries were forever frozen with the introduction of the Euro, countries that were doing well continued to do well and countries that struggled continued to struggle. More than that, there was no longer any currency flows to hide behind: an orange didn't cost X Drachmas and Y Deutschemarks, it cost Z euros and while Z might be higher in Cologne than Athens, there was no advantage from a cheap Drachma to sell oranges for expensive Deutschmarks. Strong manufacturing operations in Hanover could no longer be undercut by scrappy outfits from Pesaro. So trade protectionism needed to come from somewhere else.
Greece is already in the shitter. Macedonia is not. Macedonia would like to join the Grand Experiment and when they do, their place in the sky will be frozen forever (theoretically). So it behooves the Greeks to keep them out until their economy is in the shitter so that they can still compete against Macedonia (among others).
Greece, of course, is already a member of the EU. And they've been on a severe austerity budget from the rest of the EU (IE Germany). And it's been working. But they're about to need more money.
And dollars to donuts, Merkel told Tsipras to get out of the way in exchange for favorable treatment, and Tsipras is willing to go for it despite a challenge from his own 'winger adversaries, and it all boils down to who can crack more boons out of Germany and France using whatever means necessary.
So yeah. It makes Greece look petty AF. But you have to keep in mind that the Euro kinda made them a vassal state of Germany 20 years ago and they're starting to get bitchy about it.
Looking petty is the least of their problems.