Different people have different views on whether consumption of meat by a Sikh is allowed. Some feel it is prohibited while others feel there is no prohibition. Let us make an effort to understand what Gurbani says. Those who think meat is not to be taken by a Sikh quote the following:
ਜਉ ਸਭ ਮਹਿ ਏਕੁ ਖੁਦਾਇ ਕਹਤ ਹਉ ਤਉ ਕਿਉ ਮੁਰਗੀ ਮਾਰੈ ॥੧॥ ਕ ੧੩੫੦
When the One God resides in all why do you kill the birds (SGGS, p 1350)?
The immediate reaction on reading the hymn will be that Bhagat Kabir Ji is dissuading people from eating meat. Firstly there is only mention of killing and not eating; Secondly he mentions God being present in all including the bird being killed so there must be a context to this Shabad. The context is clear when we read further:
ਪਕਰਿ ਜੀਉ ਆਨਿਆ ਦੇਹ ਬਿਨਾਸੀ ਮਾਟੀ ਕਉ ਬਿਸਮਿਲਿ ਕੀਆ ॥ ਜੋਤਿ ਸਰੂਪ ਅਨਾਹਤ ਲਾਗੀ ਕਹੁ ਹਲਾਲੁ ਕਿਆ ਕੀਆ ॥੨॥
You catch the living creature and kill the body as sacrifice to God; But God’s light in the creature is indestructible; so what do you sacrifice?
It is therefore clear that the context is sacrifice of creature to propitiate God or any other deity. Hence Kabir Ji is dissuading people from sacrifices. Bhagat Kabir also says in a Slok (Couplet):
ਕਬੀਰ ਭਾਂਗ ਮਾਛੁਲੀ ਸੁਰਾ ਪਾਨਿ ਜੋ ਜੋ ਪ੍ਰਾਨੀ ਖਾਂਹਿ ॥ ਤੀਰਥ ਬਰਤ ਨੇਮ ਕੀਏ ਤੇ ਸਭੈ ਰਸਾਤਲਿ ਜਾਂਹਿ ॥੨੩੩॥
Whosoever takes Marijuana, fish and alcoholic drinks; all his pilgrimages, fasts and performance of religious practices shall go waste (SGGS, p 1377).
Here Kabir Ji is dissuading people from taking intoxicants and non-vegetarian food.
This is a stand alone Slok and its context needs to be found from what Kabir Ji says elsewhere. He says:
ਸੁਆਦ ਲੁਭਤ ਇੰਦ੍ਰੀ ਰਸ ਪ੍ਰੇਰਿਓ ਮਦ ਰਸ ਲੈਤ ਬਿਕਾਰਿਓ ਰੇ ॥ ਕਰਮ ਭਾਗ ਸੰਤਨ ਸੰਗਾਨੇ ਕਾਸਟ ਲੋਹ ਉਧਾਰਿਓ ਰੇ ॥੩॥
Under the influence of taste and pleasures of sensory organs, one indulges in intoxicants and tasty food that take one to vices (SGGS, p 335).
It is well known that indulgence in fish etc and intoxicants leads to vices like violence and lust satisfaction outside marriage or even overindulgence with the spouse. If we read this with the above Slok it appears that Kabir ji is asking people to understand that indulgence like this will negate all your religious practices.
Further we find that in the SGGS there are specific instructions to avoid intoxicants. The third Guru says
ਮਾਣਸੁ ਭਰਿਆ ਆਣਿਆ ਮਾਣਸੁ ਭਰਿਆ ਆਇ ॥ ਜਿਤੁ ਪੀਤੈ ਮਤਿ ਦੂਰਿ ਹੋਇ ਬਰਲੁ ਪਵੈ ਵਿਚਿ ਆਇ ॥ ਆਪਣਾ ਪਰਾਇਆ ਨ ਪਛਾਣਈ ਖਸਮਹੁ ਧਕੇ ਖਾਇ ॥ ਜਿਤੁ ਪੀਤੈ ਖਸਮੁ ਵਿਸਰੈ ਦਰਗਹ ਮਿਲੈ ਸਜਾਇ ॥ ਝੂਠਾ ਮਦੁ ਮੂਲਿ ਨ ਪੀਚਈ ਜੇ ਕਾ ਪਾਰਿ ਵਸਾਇ ॥
One person (like the bartender) brings the intoxicant, another takes a cup from it; by drinking it he loses his power to think and acts as if mad; he is unable to distinguish the good from bad and is pushed away from the Master; by drinking it the Master is forgotten and one is punished in His court, Do not take such a drink if it is within your power. (SGGS, p 554).
There is therefore specific injunction against intoxicants, but it is not so for non-vegetarian food. For example Guru Nanak says:
ਅਭਾਖਿਆ ਕਾ ਕੁਠਾ ਬਕਰਾ ਖਾਣਾ ॥ ਚਉਕੇ ਉਪਰਿ ਕਿਸੈ ਨ ਜਾਣਾ ॥
You eat the meat of the goat killed the Muslim way but talk of piety (SGGS, p 472).
Guru Sahib is pointing out the hypocrisy of the Hindu. If he wanted to prohibit non-vegetarian food, he could have just said meat or goat and not meat dressed the Muslim way, which is also an edict in the Sikh Reht Maryada. Such meat is taboo for the Sikh.
There is thus no injunction against eating meat but also no advice to eat it. According to Guru Nanak:
ਮਾਸੁ ਮਾਸੁ ਕਰਿ ਮੂਰਖੁ ਝਗੜੇ ਗਿਆਨੁ ਧਿਆਨੁ ਨਹੀ ਜਾਣੈ ॥
The ignorant persons, instead of acquiring knowledge or meditate, fight whether to eat meat or not (SGGS, p 1289).
In other words the Guru asks the Sikhs not to make it an issue. It is to be kept in mind that we are not to take food or drink:
ਜਿਤੁ ਖਾਧੈ ਤਨੁ ਪੀੜੀਐ ਮਨ ਮਹਿ ਚਲਹਿ ਵਿਕਾਰ ॥੧॥ ਰਹਾਉ ॥
That is harmful for the body and causes vicious thoughts, Pause, (SGGS, p 16).