Last Hearth
Member
Two things:
From the POV of the characters, that requires you to believe Joffrey is illegitimate. Of course we know he is, but they have to assess the wortiness of the claim without having studied Mendel in High School or having seen Ned's/Jon's evidence.
From the POV of us readers, we know that power lies where men believe it lies. Robert usurped the throne, so who's to say Stannis is legitimately the heir? If you figure all bets are off, go with whomever you like. I mean, by modern sensibilities, succession and rule by right of kings and lineage is a load of crap anyway. Robb at least had people declare him king (although he was only in a position to be declared by his own birth in the first place).
But that's my point, modern rules of succession is not different, it's exactly the same.
If the president dies the vice president succeeds him. The only thing different with modernity is that the change of regime is different, we have elections rather than right of conquest. But rules of succession within a regime is still expected to be followed.
The Targaryens won a right of conquest 300 years ago, that's like saying Bush was the election in 2000 and 2004. But Obama won in 2008 and 2012, that's like saying the Baratheons took over by right of conquest. Once you lose by right of conquest you're done. You have no claim. Dany has no claim. Her only claim will be through another conquest (even she knows this, which is why she's building an army).
Stannis's claim is no different than Biden's would if the president dies, and his level of annoyance at the people who won't recognize this is every bit as deserved as Biden's would be if people acted to deny him the presidency.
When Robert died, given that he has no legitimate children, Stannis is the heir.