Complicated is no synonym of conspiracy theory, see Reality vs Fantasy.
Pointing out someone's contradictory arguments is definitely not ad hominem attack.
The argument started by person A stating a fact and person B claiming it's a conspiracy.
I stepped in and said it's no conspiracy.
Person B says, I didn't mean conspiracy, I meant it's more complicated
I respond to person B if you meant complicated, you would have said something along those lines. Instead you said conspiracy theory.
Calling out bs is not an attack on the person, it's a reflection to what they say.