The music group was hired as the headlining gig for TVP's "New Year's of Dreams" show, and when they finally hit the stage ... all 4 members came out wearing rainbow armbands. It seems they kept them on for a good while, too, as they went through their set.

Of course, that sparked outrage among Poland's Law and Justice Party (PiS), which is in power at the moment -- and which has taken on very strong anti-LGBT views and policies ... trickling throughout much of the country and embraced by several citizens as well.

One such member of PiS, Marcin Warchol, expressed his indignation at the BEP's accessories, writing ... "LGBT promotion in TVP2 . DISGRACE! It’s not a New Year’s Eve of Dreams but a New Year’s Eve of Deviance."

The funny thing is that TVP is, more or less, a state broadcaster -- they regularly air programming that aligns with PiS ... and the Black Eyed Peas were presumably hired by someone working there/with ties to the ruling party. So ... this is kinda on them.

Will.i.am caught wind of the backlash and responded, writing ... "#WHEREStheLOVE??? Unity, tolerance, understanding, oneness, respect, diversity & inclusion…THATS LOVE…people are people & we should all practice to honor & love all the different types of people on earth & learn from them…I LOVE YOU your country…"

He further addressed the matter on video, posting a clip of himself talking about why they did what they did -- and it all comes down to trying to reach people who don't see eye to eye.