It's likely they're referring to the effect outdoor cats have on bird populations. They're credited with the the extinction of 63 species: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5056110/
Nobody is claiming that humans haven't caused damage to the ecosystem. But you're just spouting a whataboutism when we _know_ that cats are also incredibly damaging when let to roam free.