What is the moral problem with this? They are'nt being killed for their stem cells/kidneys, that is obviously different. The choices are burn, bury, use or eat (ref python: if you feel guilty about eating your dead mother you can through-up into a grave afterward).
The problem is more of a slippery slope problem than the immediate case being made.
As stem cells become more useful, the demand for stem cells will also increase. Thus, we first let the embryos grow further in order to harvest more. However, since growth can only occur so far in a petri dish, the "term implantation" will occur so that the growth can be harvested for stem cells and other parts as well.
Most Monty Python references are crass and yours is no exception. Instead, I suggest: