Dtyjlui

In the chapter II : THE FIRST STEPS of Raja-Yoga non-killing is one of the requirement of Yama step

Râja-Yoga is divided into eight steps. The first is Yama —
non-killing, truthfulness, non-stealing, continence, and non-receiving
of any gifts. Next is Niyama — cleanliness, contentment, austerity,
study, and self-surrender to God. Then comes Âsana, or posture;
Prânâyâma, or control of Prâna; Pratyâhâra, or restraint of the senses
from their objects; Dhâranâ, or fixing the mind on a spot; Dhyâna, or
meditation; and Samâdhi, or superconsciousness. The Yama and Niyama,
as we see, are moral trainings; without these as the basis no practice
of Yoga will succeed. As these two become established, the Yogi will
begin to realise the fruits of his practice; without these it will
never bear fruit. A Yogi must not think of injuring anyone, by
thought, word, or deed. Mercy shall not be for men alone, but shall go
beyond, and embrace the whole world.

Does it mean a person should avoid non vegetarian food to be successful in Raja Yoga? Although the above statements support it but I found no explicit statements of avoiding non vegetarian food.

According to Hatha Yoga Pradipika, Chapter 1, one should not take non-vegetarian food during Raja Yoga. Hatha Yoga is said to be staircase for Raja Yoga. By practicing it, one can attain Raja Yoga.

शरी-आदि-नाथाय नमो|अस्तु तस्मै

येनोपदिष्ह्टा हठ-योग-विद्या |

विभ्राजते परोन्नत-राज-योगम

आरोढुमिछ्छोरधिरोहिणीव || १ || || १ ||

śrī-ādi-nāthāya namo|astu tasmai

yenopadiṣṭā haṭha-yogha-vidyā |

vibhrājate pronnata-rāja-yogham

āroḍhumichchoradhirohiṇīva || 1 || || 1 ||

Salutation to ādinātha (Śiva) who expounded the knowledge of Haṭha Yoga, which like a staircase leads the aspirant to the high pinnacled Rāja Yoga.

In the later section of this chapter, various foods are mentioned that should be avoide by a Yogi and that include non-vegetarian food too.

कट्वाम्ल-तीक्ष्ह्ण-लवणोष्ह्ण-हरीत-शाक-

सौवीर-तैल-तिल-सर्ष्हप-मद्य-मत्स्यान |

आजादि-मांस-दधि-तक्र-कुलत्थकोल-

पिण्याक-हिङ्गु-लशुनाद्यमपथ्यमाहुः || ६१ ||

kaṭvāmla-tīkṣṇa-lavaṇoṣṇa-harīta-śāka-

sauvīra-taila-tila-sarṣapa-madya-matsyān |

ājādi-māṃsa-dadhi-takra-kulatthakola-

piṇyāka-hingghu-laśunādyamapathyamāhuḥ || 61 ||

Bitter, sour, saltish, hot, green vegetables, fermented, oily, mixed with til seed, rape seed, intoxicating liquors, fish, meat, curds, chhaasa pulses, plums, oil-cake, asafœtida (hīnga), garlic, onion, etc., should not be eaten.

And at last it says following:

न वेष्ह-धारणं सिद्धेः कारणं न छ तत-कथा |

करियैव कारणं सिद्धेः सत्यमेतन्न संशयः || ६९ ||

पीठानि कुम्भकाश्छित्रा दिव्यानि करणानि छ |

सर्वाण्यपि हठाभ्यासे राज-योग-फलावधि || ७० ||

na veṣa-dhāraṇaṃ siddheḥ kāraṇaṃ na cha tat-kathā |

kriyaiva kāraṇaṃ siddheḥ satyametanna saṃśayaḥ || 69 ||

pīṭhāni kumbhakāśchitrā divyāni karaṇāni cha |

sarvāṇyapi haṭhābhyāse rāja-yogha-phalāvadhi || 70 ||

āsanas (postures), various Kumbhakas, and other divine means, all should be practised in the practice of Haṭha Yoga, till the fruit—Rāja Yoga—is obtained.