You couldn't be more wrong. Abaddon has resisted the Chaos gods for 10,000 years he knew the mistake Horus made and is one of the most self controlled individuals in the 40k universe, regardless of Talos.
And what was the mistake Horus made?
Don't get me wrong, I agree with you that people are hard on Abaddon, mostly because they don't actually read the material, however Abaddon has the luxury of not having to make damning pacts with the Chaos Gods because he doesn't have to fight the Emperor.
Anyway, Horus spent an eternity in the realms of the Chaos gods leading their armies in battle to earn their favour (Vengeful Spirit), the fact he didn't die, devolve, or submit to any one god and become a daemon prince, by your own metric, shows that he has the same 'self control' as Abaddon.
I think there's one thing that always stands out to me that makes the bolded statement almost too... incomplete. People generally seem to forget that Horus was literally on his death bed. He was a goner.
The selfish act to save himself started that ugly pact from day one. (Thanks to those dirty Word Bearers and their dirty xenos shiv). In those moments Horus was severely mislead into delusional fairy tales about how the Emperor is doing it all for himself, etc, etc. (If you recall Horus in these death thrashes was under the heavy influence of the chaos poisoned blade.)
It's at that point really, on his death bed, in chaos delusional dreamland, that Horus says, 'Okay, give me more of the kool-aid, and sign me up!'
All that time, Abaddon never really had those dilemmas to deal with. If we step back to those moments, recall that Abaddon festered. Why wasn't that selfish Emperor here? Why was he holed up in his castle on Terra while his favoured son is dying for His cause?
There are -very- old pieces of fiction that are hard to find now. I probably read them... 10 years ago if I'm guessing. I was always struck with the images of the final moments of the (abbreviated) description of Horus' very final moments vs. the Emperor.
I don't want to spoil anything here, but suffice to say according to that very old fiction, Horus was.... severely manipulated. (I don't know if that's how it will play out with the modern authors. Much has changed.)
Abaddon had none of that on his plate. He truly took his own path. There is a far more recent passage in the HH series that shows Abaddon kind of... signing up to join a very bizarre, dark group of entities that have been watching Abaddon. They make a pact with him of sorts. He seems to 'owe' service to these dark warp demi-gods. He will become one of them perhaps. He seems to suit a certain make up that they look to enlist. It's an interesting side note to this conversation. But it appears Abaddon will have a dark, violent club to join in the afterlife (not like his current life is full of cookies and fairy tales.) This club, for lack of a better term, seems to operate on the outskirts of Chaos.
Abaddon definitely walks his own path. Chaos needs him but can't control him like Horus was. Frankly if it weren't for Horus I don't personally believe Abaddon would have went astray. But Chaos made sure to show Abaddon how little the Emperor cared for any of them, and that started the fires in Abaddon's heart.