This is true history and it should be stated by Christians before critics have to. The text has been used that way, the users were often sincere, and people died. No amount of contextual reading undoes that, and a defense of these passages that skips it is not worth reading.
Two things follow. The first is a distinction the misuse always has to violate: on the Bible's own account this was a specific judgment on a specific society at a specific moment, announced centuries in advance, executed once, and never authorized again. Nothing in the Old Testament treats it as a standing policy, no prophet calls for its repetition, and the New Testament forecloses it, which is exactly what the rebuke to the disciples who wanted to call down fire is doing.
Every historical misuse required treating a closed event as an open permission. The second is that this cuts against a certain style of defending the text. If the practical danger is the deserved-it framing, then defenders should be more careful with it, not less, and should notice that the Bible itself immediately turns the same standard on Israel, which is the one move that makes the framing unusable as a weapon against somebody else.
A reading that leaves you feeling secure about your own side has already gone wrong.