The main issue with GPLv3 is the so-called Tivoization clause. It basically states that if you have a product that ships with any GPLv3 software, you need to give your users the ability to install a modified version of anything you included that's GPLv3. Which basically means you can't lock down your device.
That's totally fine if you're talking about a workstation, laptop, or server. But it's a big security risk on an embedded system like a smart TV, mobile phone, or game console - both from an IP protection point of view, and also from a botnet/pwning point of view.
FreeBSD (and others presumably) don't want their users to need to worry about accidentally installing something from the core system and finding themselves in violation of the GPL.
That's a rationalization though, not the reason. FreeBSD's GPL "exorcism" efforts had been going on long before FSF started floating ideas about GPL 3.0.
That's totally fine if you're talking about a workstation, laptop, or server. But it's a big security risk on an embedded system like a smart TV, mobile phone, or game console - both from an IP protection point of view, and also from a botnet/pwning point of view.
FreeBSD (and others presumably) don't want their users to need to worry about accidentally installing something from the core system and finding themselves in violation of the GPL.