Dave,

Still no comment on why this only happened when Jeremy Corbyn was voted leader? An inconvenient significant fact maybe?

No Dave. The complaints suggest that the problem is mostly with the far Left.
Political extremists are notoriously intolerant.

Asking why is inviting speculation.
The fact is that there have been a stream of complaints emanating from Labour and the acknowledgement that there is a serious problem.
That is my case, and it is proved.
You suggest that other parties are at least as bad, but there is no evidence for that.
There are no streams of complaints from them.

Your assumption is based on nothing but preconception and prejudice.
No evidence at all.
All the evidence points the other way.