The idea is that one can obtain animal products as a gift which absolves them of ethical responsibility.
I've never met someone that accepts non-meat animal products as gifts but doesn't consume animal products in some other context. So this is an unusual edge case and isn't the justification for the majority of carnism.
As previously mentioned, unethical things need to happen in the pursuit of making such a farm actually productive in any capacity, so all the arguments on this page apply.
If you consider the implications of an action based on the amount of suffering and well-being it produces, accepting gifts of animal products means that "your uncle" (or whoever is giving the animal products) is still deriving personal value from those animal products in the form of a gift to you and is, therefore, more likely to continue paying for animals and therefore their abuse and slaughter.
Ultimately, it's up to you to decide how ethical you want to be and how much you want to lend tacit approval to that market.