A lovely Christian friend of mine was about to buy hot sausage rolls for her and her husband one lunchtime when she spotted a man sitting on the street. He looked like someone in need and she was reminded that Jesus said whenever you 'feed the hungry' (paraphrased, but you get the drift) you are feeding me. So she bought an extra sausage roll and offered it to the man. He very politely refused on the grounds that he doesn't eat pork. My friend's response was to smile to herself - and as she recounted the story to me later she said, 'of course he doesn't eat pork - he's Jesus'! 
As to the man mentioned in the OP - when you have very little materially it becomes very important to hold on to your sense of who you are and being vegetarian is clearly a major part of this man's identity.
At Christmas I cooked a halal meal (chicken) for our Muslim guests, a traditional Turkey and trimmings meal for our Malaysian guest, but the homeless man I was cooking for loves birds and said he'd rather not have a Christmas dinner if it was going to be a bird. I made him roast beef! 
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Would you think it was odd if a younger person wanted to befriend you?

