Taking a weapon means self defense and is what you would have done
That is your opinion.
It is, not, however, the way the law sees it, at least not in UK.
Even here, if I don’t normally carry a gun, but choose to take one along to a planned confrontation, I’m going to have a difficult time explaining why the change in my behavior.
The idea that those who initiate a confrontation have some responsibility for the results of that confrontation, BTW, is not some new or modern notion. It goes WAY back in the common law, back to where the normal method of addressing disputes was exactly what this guy did. Get your buddies together and go over and confront your enemy.
Fairly obviously, this led to a lot of breaches of the King’s Peace. So the common law addressed the issue by making the initiator of the confrontation at least partially responsible for how it turned out. Under the law he was supposed to go to the King’s representative for justice rather than go for the do it yourself version.
You may not like this, but your opinion does not change the law.