It's always difficult to prove a negative... When you put forward a farfetched 'theory' it is for you to provide evidence.
Otherwise, following your logic, everything and every conspiracy theory should be assumed valid until proven wrong, which is ridiculous.
Example: The Novichok poisoning in the UK happened about 7 miles from the only lab in the country that works on these things. The UK government is actually behind it and they are framing the Russians for it. Prove me wrong.
Now, seriously, considering that bats gave us SARS and MERS, and that they harbour other coronavirii extremely similar to Covid-19 all over Southern China and down to Thailand, the overwhelmingly most probable theory is that the origin of Covid-19 will be bats, somewhere in Southern China. If you think that's not the case then it is for you to support your hypothesis.