Here is a quote from Master Ching Hai:
A lifetime commitment to a vegan or lacto-vegetarian diet is a prerequisite for initiation into the Quan Yin Method. Foods from plant sources and dairy products are permitted on this diet, but all other foods from animal sources including eggs should not be eaten. There are many reasons for this, but the
most important comes from the First Precept, which tells us to refrain from taking the life of sentient beings, or "Thou shalt not kill."
Not killing or otherwise harming other living creatures is of obvious benefit for them. Less obvious is the fact that refraining from harming others is equally advantageous for ourselves. Why?
Because of the law of karma. "As ye sow, so shall ye reap." When you kill, or cause others to kill for you, in order to satisfy your desire for meat,
you incur a karmic debt, and this debt must eventually be repaid.
This is one reason it is required to learn the meditation.
They are facts. Click
Here and
Here for articles about the Food and Agriculture Organization department of the United Nations explaining the detriment of raising animals for meat.
Here is the actual report from the FAO.
Also,
here is an article explaining how raising animals for meat causes world hunger.
This is just scratching the surface.
I hope this helps to illustrate why being vegetarian is required to learn the meditation. It is in no way harmful to anyone, it is very beneficial to everyone.
If you have any more questions about why vegetarianism is required for the method, please feel free to ask.