The UPA was the ONLY military force that fought FOR UKRAINE in WW2.
So what? That doesn't mean it is worth idolatry.
There is absolutely no evidence that there were orders from the UPA commanders to massacre Poles and other minorities. (In fact, quite a lot of UPA fighters were themselves ethnic Russians or ethnic Jews.) An attempt on the life of a civilian - of any ethnicity - had to be, according to the UPA disciplinary code, punished by firing squad.
Of course, during a ruthless guerilla war, all sides seek those who aid the other side, and deal with those people quite brutally at times. Polish Armiya Krayova did that to whoever they thought were aiding UPA, and UPA retaliated by the same actions, yes, sometimes brutal, dirty, bloody.
But such massacres did occur even if you wished to pretend otherwise. The Kresy was a vibrantly multicultural area before WWII. After WWII it was left homogeneously Ukrainian: Jews, Poles and Germans need not apply. Of course the Nazis and the Red Army did the brunt of the ethnic cleansing, but the UPA certainly doesn't have clean hands. I can't respect it as an organization because even from its days as a terrorist organization before the War it proposed only simplistic solutions, i.e Ukrainian nationalism to an area that demanded complex answers.
While I sympathize with some of the ideals of the UPA, I find the ubiquitous Bandera statues of Western Ukraine to be as ridiculous as Lenin statues of Eastern Ukraine. Why can't people simply live - why do they need an idolatrous civil religion and the accompanying instruments of liturgical worship? It doesn't matter whether it is Marxism-Lenism or X nationalism.
Still, just like AK are heroes to Poles, UPA are heroes to me, and as long as I live I will celebrate their memory.
My grandfather actually fought in the AK and his version of events is bit different. I've never encountered triumphalism or reveling in the glory of Poland from him. In fact I've only ever heard him express sadness that most of those he had to kill in combat were likely young people like himself that had absolutely no desire to be engaged in warfare. They were simply born in Germany or the USSR and conscripted to fight. I've never seen that sort of nuanced memory from a nationalist. Never.
But I can see why many Orthodox Christians would venerate the UPA as they are not in fact real Christians. They are nationalists and Orthodox Christianity is a mere adjunct to this primary faith. If the state religion of Ukraine became Buddhism tomorrow, I'd expect the vast majority of today's "Ukrainian Orthodox" to be writing about how Vladimir the Great had been a crypto-Buddhist and such.