Because one can be pinned down to government involvement, while the other can't.

It's the classic CCP defense: "We're not an authoritarian country, you're just racist!".

EDIT: not saying that it was or wasn't a lab leak, but as soon as the government shoots down the possibility with "you're racist", I immediately get suspicious. The same way that I get suspicious when Israel shoots down criticism with "you're just anti-Semitic". It's basically gaslighting with identity politics.

It was never the theory that was racist, it was the amount of evidence behind it.

If "there's a virology lab there" was all the evidence you needed to assert it was a lab leak, chances are it's because you're racist. That's why early on, this theory was most popular with far-right reactionaries.

Meanwhile, what's been the origin story of every similar virus? Animal trade. That's why early on, this theory was most popular with actual scientists who were actually qualified to have an opinion.