You know the type.
Every statement the member makes is written as a debate-ending truth.
More savvy and empathetic members know it’s best to preface or caveat their statements i.e.:
“In my experience…[xyz]”
Now a debate can continue with conflicting sources of information, experiences, and opinions without heading into an argument. Prefacing your belief with the source of that belief allows an ongoing discussion.
We once wrestled with this problem recently in a small community of practice. A handful of Declaration Dans were causing arguments and ending discussions simply by their belief in their own rightness.
We first tried soft messages to reason with them, but these were largely ignored. So we tried social pressure instead. We created a cartoon character called Declaration Dan which appeared on the homepage sidebar with a short warning to “Don’t Be Declaration Dan”. The image was clickable and gave (made up) examples of Declaration Dans and what they should do instead.
Two volunteer members also helped by calling out the next few examples of Declaration Dan they saw. Other members began picking up on it too and referring to similar comments as Declaration Dan.
Soon becoming a Declaration Dan was a term of light mockery and a sign of one’s insecurity.
It didn’t completely eradicate the problem. But it drastically reduced it.