I am not against meat-eating, and I believe anyone who is extremely active or their livelihood depends on physical exertion throughout the whole week i would reccommend to eat meat if they have no interest in spirituality. They will have more energy to sustain them throughout the week.
However eating meat increases Rajas and Tamas which unsettles the mind. If you are interested in spiritual practices an over-active mind will be a hindrance to progress further in yoga. Rajas is the active-creative force and Tamas the negative-destructive aspect. The balance between them both is called Sattva, and this helps to keep the mind calm and greatly aids in yoga practise. Therefore yogis have always promoted the consumption of Sattvic foods in general. Anything which disturbs Sattva like coffee for example is also not a help. Swami Sivanada produced a list of the different catagories of foods and their effects in many of his free books online.
There is a video on youtube of Gordon Ramsey who stayed in an ashram for a few days where no meat was served. He has always been anti-vegetarian but had to admit that he began to feel more relaxed not eating meat: https://www.youtube.com/watch?v=URR8tXf3IXY