Hey, I got into an argument on reddit recently (as you do) with some anti-Catelyn bashers, and one of their common circlejerks is that Jon has no claim, and Cat is being paranoid. I’m open to the possibility that I’m wrong and she is just crazy, but i was wondering if there are any in universe examples of bastards causing problems besides the obvious blackfyres as they were ‘legitimized’ 🙄

It’s not true that bastards never inherit – Alyn Velaryon did, Bran considers making Larence Snow the heir to Hornwood, etc. – but it’s extremely rare. So Catelyn’s not entirely wrong about the potential domestic politics in the long-term. 

But she is taking the worst-case scenario. The Blackfyres are at one end of the spectrum, but the Longwaters are another possible outcome, and there are clearly others (as we can see from Westerosi heraldry). 

I wouldn’t call Catelyn paranoid, because I don’t think her feeling toward Jon is primarily motivated by fear.