It’s not that EVERY full stop is passive aggressive, it’s about interpreting tone.

So for example, when I text my parents and say, “Thank you for the invite, we’d be happy to come over for dinner next Monday!” and my dad replies, “Great.” That looks passive aggressive.

He doesn’t mean it that way, tone interpretation from short texts just isn’t something he’s fluent in like those of us who’ve been texting (or IMing back before texts) most of our lives.

If he had said “Great” that would be fine, as would “Great!” But “Great.” is interpreted as sarcastic and/or passive aggressive.