First, I'd like to correct myself: La Verrier and Adams' calculations WERE wrong. Turns out they had used something called Bode's Law to predict the position of the planet Neptune.
https://en.m.wikipedia.org/wiki/Titius%E2%80%93Bode_lawProblem was, Neptune didn't follow this law, as it turns out that it's much closer to the sun than the law predicted. This was apparently the first planet to do so, which is a big part of why Bode's Law has been superseded today.
So, both La Verrier and Adams started off on the wrong foot, and their calculations, which were based on this hypothetical position of Neptune, were thrown off as a result. The planet WAS basically found by pure luck.
But does that invalidate the prediction made using the theory of universal gravitation? I don't think it does. Yes, they got the position wrong. Yes, it could very well have been pure luck that the planet happened to be in the neighborhood. But it was still based on the hypothesis that, if Newton was correct, there should be a large mass out there perturbing Uranus' orbit. And, wouldn't you know it, there it was.
It's interesting that you bring up Walker. I read that article from start to finish, and he mentioned a fellow named Lalande quite a bit, and it turns out Lalande had actually spotted neptune in 1795, and didn't realize it. He used this, along with other possible prediscovery sightings , and observational data gathered in the 9 or so months of observation of the planet Neptune to help create a more accurate model of Neptune and it's orbit.
Claims of dishonesty with Adams. You can say that it appears to be dishonesty, but Adams was described as 'Diffident', or lacking in self confidence. And his predictions of Neptunes position certainly seem to support that, as he was jumping all over the place. So, you say 'Dishonest', I say, 'a man who couldn't make his calculations fit with reality and kept changing it until he could'.
Also, he openly stated that he though La Verriere deserved the credit and that he wasn't sore about. Doesn't sound like someone dishonest to me.
Interestingly, it was La Verriere that first noticed that the orbit of Mercury didn't quite line up with Newtonian mechanics. That's how we got to the whole 'planet Vulkan' bit, until general relativity managed to explain Mercury's orbit. Can't wait for Tom to jump on THAT tidbit.
Science advances due to it's failures as much as it's successes. Neptune showed us Bode's law was more like a suggestion, and Mercury showed us we had an incomplete picture of gravity.
Flat Earth can't even agree on a goddamn map.
Which one do you expect I should take seriously?