They didn't hate Unix because it was open, but their hatred of a more open system does make them look a bit ridiculous: Any system tied to a single company is doomed anyway, either to the company dying or the company discontinuing it and/or turning it into something you can't stomach. (Microsoft lives, but how happy are MS-DOS partisans these days?) It kinda taints their technical points with a whiff of fanboyism, a naïve partisanship and attachment to entities that didn't give a shit about them.