I've written about this pretty extensively: https://www.hnsearch.com/search#request/all&q=by%3Asillysaur...
It's an interesting contrast in cultures that you phrase it like "Why do you think Telegram lies more than TextSecure advocates?" .... As far as I'm aware, TextSecure advocates haven't lied at all. TextSecure's interest is in security, whereas Telegram's interest seems to be in money and power.
Current implementation of telegram api is prone to MiM attack but I would not consider TextSecure completely safe app
I just don't know what to say to this. Telegram has been proven insecure, TextSecure hasn't. Telegram isn't designed by cryptographers, TextSecure is. There is absolutely every reason to assume Telegram is broken.
Each of these messengers is safe to passive listening.
This is mistaken because Telegram has been proven vulnerable to MITM attacks. Even after they patch this latest security problem, it would be very unwise to trust them.