Law? These are people who have access to your data, how am I, a stranger, any different from any other stranger who have access to your data? Would it be OK if I indirectly obtained your password and use it to access your data or something?

Mind you, I was speaking in general about people who claim they don't care about their privacy, or about these companies collecting their personal data, or having a history of their private messages, etc.

How can you not care about them saving your conversations in plain text, but then suddenly care about it when I ask you to show it to me? The only difference seems to be that I'm actively, personally, directly asking you for it, but ultimately it would be the same outcome.