IF I'm holding a weapon while speaking to an NPC and using the left mouse button to advance the dialogue, the weapon fires or stiffens forward, which can hurt the character. This can knock them about, too, making it potentially dizzying to keep looking at them while I talk.

I'd like to request a logic gate producing the result asked for in the title. This way I can speak with Ingot without worrying for his well-being- or that of my lunch.

This is interesting - most NPC's you can talk to via the dialogue system are invulnerable to damage, but I think ingot is the main exception. I'd have to second the notion of disabling attacking while in dialogue, since it doesn't seem intentional.

I do think that this should be an option (for speedrunners when more and more hurtable/enemy NPCs have dialog) so if you are casual and just want to read or also casual and just want to destroy

Yes, it is quite a problem but you can still read dialogues safely by pressing space instead of left clicking