This is the sort of counterargument I'd have liked to see instead of disagreement-driven downvoting, yes.
You disagree over opinions. Should Signal be an appropriate system for discussing classified data? I'd say no, you might say yes, we disagree and debate.
Legally, is Signal an appropriate system for discussing classified data? No. Unless you believe in alternative facts, there is no point to disagree on, it's just a fact that it is not legally an appropriate system for what they did.
And then swiftymon lied and used "evidence" to bolster their lie that didn't even agree with their lie.
I could assert that you're lying, etc - as you're effectively committing the same sin as the poster who originally got downvoted - but that wouldn't be having a conversation; it'd be a rude refusal to tolerate a conversation. I encourage you to assume good intent and engage instead of hurling accusations at people - even if they're new accounts.