I don't think people actually think about what a counterfeit really does before blatantly saying "they are bad" or "they will kill magic".
Counterfeits are cheap, which, because magic is based off a pay-to-win concept, (Look at guildgates and shocklands and many more) counterfeits give new and old players a way to have fun with expensive cards.
So? Your card is real and your opponent's isn't? They can't afford a real one so you won't let them use it? Most people in this thread alone are pretty butthurt.