but when there are 10 of us
In a single group, riding 2 abreast, so 5 bikes in a row with say 1 bike gap making a 9 bike long stream of bikes riding 2 abreast on a public road when there is not a sanctioned event on. I can see why he may have been unhappy.
But that does not excuse any dangerous actions on his part. Inconsiderate road users are an annoyance. Dangerous ones unacceptable.
Although if the road really was not suitable to be passing on, and remember he probably drives up it a lot so has less feeling of risk when overtaking (which can be bad), then I am all for slower road users using blocking tactics to keep themselves safe. Unfortunately the people they are having to act against don’t normally see it that way.