Why shouldn't we?
It's not like Google didn't do such things before.
The BigCo can't typically make any comment when this happens - merely say 'we have investigated and decided to uphold the ban', and then they look unreasonable.
Sometimes the unreasonable thing is done by malware on the users computer/phone, so even the user isn't aware, but from BigCo's perspective it all looks the same.
BigCo processes are still opaque, but often the outcomes aren't as unreasonable as they seem.
Where did "at least half" come from? Is this a statistic derived from factual information or just some gut feeling?
It was never the intention of "the poster" to "share child porn". They never had any to begin with. It's just algorithms doing things, then blaming the owner of the device for what Google (incorrectly) perceived them to be doing.