Short quote: have a nice day!
Sometimes it is hard to tell the difference between innocuous solicitudes and a lecture and sometimes it isn't. Either way, jumping from neutral to a fourth gear of high-handed pissed-offedness, while probably being of some cardiovascular benefit, seems equally presumptious as the lecture and until the true nature of the reposte can be determined would probably best be fended off with a nod and a half-smile.
On the wider topic of prayer, I, for one, would be flattered (and, possibly, sort of relieved) if religious friends were to remember me in their prayers. It may work (I doubt it, but you never know), but, more than that, it is an expression of friendship – and, as such, it is to be welcomed, relished and celebrated, however strange the form it takes.