Especially when we, as Christ followers/servents are to crucify our flesh and live by the Holy Spirit. So I too, would be very weary of any Christian that is spewing forth fleshly sermons, advice or anything.
Of course, we need to have grace, cause lets face it, we all slip up from time to time and our flesh gets the better of us. But when all you see is continual flesh and not Holy Spirit then you know something is wrong. And that is the time to get on your knees and start praying for that person. Because fleshly Christians usually also have hard hearts.