When you wrote:
It came across as though you were claiming those arguing RaW and presenting cases where weapon stats have changed as being stupid and unable to play the game for fun.
May I direct you to the Space Marine and Imperial Guard shotguns? They have different stats without an explaination as to why, and the rules are both from 5th edition codecies. We don't know why they are different, we just accept what is written in the different codecies and get on with the game. Arguing that the BA Demolisher Cannon is "supposed" to be a Blast weapon is no different than arguing that the IG shotgun should be S4.
I don't recall anyone saying that they are playing it as non-Blast or any who are forcing their BA opponents to play it as such. I had mentioned a hypothetical situation where a player doesn't know about the Demolisher Cannon outside of the BA codex, and another situation in which I would play by the rules as written if using a BA Vindicator. Did I miss the post where someone said they would actually require their BA opponents use use it as written?