"What really amazes me is folks who complain about SHA1 being insecure, without even having an understanding of how preimage attacks work.

Either explain to us the attack vector against actual SHA1 certificates that could result in wide-spread faking of certificates, or withdraw your claim.

Your explanation needs to also explain how this attack could cicumvent the various defense-in-depth official and unofficial checks (certificate transparency, certificate revocation lists, limited time validity)."

I hope we can at least agree that this is not the way to argue about security protocols at least when it comes to crypto.