You misread your parent post. Bgorrman didn't say that WeChat being insecure means that iMessage and Whatsapp are insecure. Bgorrman questioned if we have reason to believe that iMessge and Whatsapp are more secure than WeChat.

A implies B & C is not the same as asking whether B & C share the same qualities as A.

You actually created a strawman in order to say that your parent had a false equivalence.