You've shifted the goal posts in this sentence. Previously, you said there was no evidence of black holes. Now you're upped the scale to demanding proof.

The previous commenter wasn't claiming that LIGO detections were proof of black holes. They said that they were evidence of black holes.

The LIGO detections, by all reasonable metrics, would certainly qualify as evidence of black holes. Of course, I agree with your assertion that taken alone, LIGO detections are not proof of the existence of black holes. Taken with the significant body of other evidence we have, though, I would say the sum total of evidence that we have is a strong indicator that black holes exist.