I'm not assuming people are racist because they disagree with me. I'm pointing out that their gut-reaction accusation of calling others a "chinese bot" is racist.
This has nothing to do with disagreeing. I made no assumptions, I pointed out racist language and behaviour.

They brought up that China shouldn't have blocked initial investigations and instead of replying with any facts yourself

Other users have already engaged with them in this argument, to which they responded with racist accusations of being "chinese bots".
Since they have already shown that this is how they behave, and since I have similarly pointed this out to them - which also resulted in childish racism as a response from them - why would I in any way validate them with civility?