Dark Magical Circle vs Red Eyes Slash Dragon

Hello, playing red eyes, in my field there is Red Eyes Slash Dragon, the effect says “ When a "Red-Eyes" monster declares an attack: You can target 1 Warrior monster in your GY; equip it to this card as an Equip Spell that gives this card 200 ATK. When a card or effect is activated that targets a card you control (Quick Effect): You can send 1 Equip Card you control to the GY; negate the activation, and if you do, destroy that card. If this card is destroyed by battle or card effect: You can Special Summon as many monsters from your GY as possible, that were equipped to this card.”, my opponent controls dark magical circle (“ When this card is activated: Look at the top 3 cards of your Deck, then you can reveal 1 "Dark Magician" or 1 Spell/Trap that specifically lists the card "Dark Magician" in its text, among them, and add it to your hand, also place the remaining cards on top of your Deck in any order. If "Dark Magician" is Normal or Special Summoned to your field (except during the Damage Step): You can target 1 card your opponent controls; banish it. You can only use each effect of "Dark Magical Circle" once per turn.”) and a monster. In my batte phase my Red eyes attacks the monster And activates his effect, so my opponent chains “magician navigation”.
The chain resolves, so my opponent summon 2 dark magician and a warrior type monster equips the red eyes. Then, After the chain, dark magical circle’s effect activates and targets my red eyes to banish him, the game dont let me negate that effect with my dragon despite the 2nd effect of dark magical circle says specifically “target 1 card”... why?