There's actually a name for people who perceive proper punctuation as being passive aggressive. They're called "morons."
Edit: in the name of further research I asked my wife, who is a non-punctuation texter, what she thought about this. Here's what I got.
Results of Conversation with Mrs. jubilationtcornpone
Me: "If someone sent you a message that had a period at the end, would you think they were angry with you?"
Her: "Like now? No. When I was younger? Yes."
Me: "Why would you think that when you were younger?"
Her: "Hmmm. I don't really know. I guess because women tend to read between the lines, even if there's nothing there. And because people like to have something to complain about and little miscommunications are an easy target."
Me: "Ok. So why doesn't it bother you now?"
Her: "Probably because I met you and you always use punctuation. You know ? She knows when he's mad at her just based on specific words he uses in texts or just the way he says something."
Me: "So if you start using punctuation, I should be concerned?"
Her: "Like if I say "I'm fine." With a period and everything?"
Me: "Yes."
Her: "Yeah. That means I'm not fine."
Me: "That's a lot of pressure to put on a period."
Her: "True."
Me: "But you already know I'm going to infer nothing from that. I probably won't even notice."
Her: "Yeah. I know. That's why l would just tell you."
Me: "Fair enough."
Her: "You're just one of those people who says exactly what they mean. There's no cryptic message or anything."
Me: "That's what I'm talking about!"
Her: "It is kind of nice actually."