I don't think there would be any templates like that in public. Companies and their support depts use what works for them, - which might not always work for you.
The general rules for de-escalating conflicts are
- reply super-fast
- encourage to take the argument private
- say you are looking at the situation
- send updates on the situation.
If you're being attacked by a mob in some sort of a brigading campaign, it's best to just ignore it.
And never swear back. Look better than the other side.
Source: years of experience in customer support ages ago.