The reason why the plural works for a Mac or a BMW is because the product is called the company name, e.g 1 BMW, 2 BMWs. So you can say, "there are multiple BMW's" because the singular is called a BMW. This is not the case with LEGO, LEGO is the company name yes but one piece of LEGO is called "a piece of LEGO" not "a LEGO" you wouldn't say "could you pass me a LEGO?" but would say "could you pass me a piece of LEGO" therefore the plural is technically "2 pieces of LEGO" not "2 LEGOs". You can say "could you pass me the LEGO" referring to the entire product but if you were talking about individual pieces, LEGO's is incorrect.
There is no discussion, or debate, it's just English.