On Android, I just finished a game where I was completely unable to target Sidisi, Regent of the Mire with any of my removal spells. I tried both Cut Down and Annoint with Affliction but the card wouldn't even let me choose it. Both attached screenshots were taken during my turn so Voice of Victory's effect would not have been active and there were no other effects in play, as you can see that I could hit Voice of Victory with Cut Down.