Sorry for sounding harsh, but it's not right to blame them for following web protocol when you don't know what web protocol is or how to make sure what you want is communicated in a protocol compliant way.
No need to be sorry TOI. But let me ask you this... Who stores my client's cached homepage in Google? Is it normal protocol for Google to receive a DMCA takedown notice and deny it while still holding my client's cached homepage in their index on proxy domains?
Since Google does not care about the work of others, by allowing proxied content to be indexed in the first place, the issue then becomes who has the right to cache/save/store my client's homepage on a different domain. My client did not give the proxy user or Google the right to display his trademarked logo on a different domain.
In other words, Google knowingly and willfully neglected the intellectual property rights of my client when they denied the DMCA takedown notices and allowed the cached pages to remain in their index.