Can you destroy a creature in response to it using its activated ability? mtg rulings

[Knight]

Can you destroy a creature in response to it using its activated ability?

[Arix]

You can, but it won't stop the activated ability from resolving.

[starfire]

yeah, once the activated ability goes on the stack, removing the source wont affect it. Only way to get it off the stack is by countering it somehow (like for example with stifle)

Also if you tried killing the creature before they activated the ability, they could activate the ability in response and it would also go on the stack and resolve even though you cast a spell to destroy the creature before they activated the ability.