They can decline to ping their own creature, but the triggered ability you give to the creature is mandatory, so if you target an opponents creature and then deal a large amount of damage to it, your opponent is forced to lose that much life
Focus Fire Rating: 4/10 Removal that only targets attacking or blocking creatures tends to fall a little short of the mark, but costing 1 mana and dealing at least 2 damage in a vacuum makes Focus Fire more than efficient enough
Syr Vondam, Sunstar Exemplar Syr Vondam, Sunstar Exemplar gets quite strong on death triggers and your exiles
What's the chance now
If youre playing an Izzet Dragons deck with cards that make treasures, such as Goldspan Dragon, Magma Opus, or Prismari Command, you can splash for bombs such as Tibalt, Cosmic Imposter