Before this week, how was it inconsistent?

And I don't see anything unfeasible about having been mauled by hellhounds and developing a general dog-dislike as a reaction

That's how I interpreted it when they've used it, but they've been so inconsistent with it that I really have no idea.

they've been so inconsistent with it that I really have no idea.

When was it inconsistent before yesterday?

Post hellounds, there was S6, with All Dogs Go to Heaven, or whatever. He didn't seem to have a problem with the dog in that episode.

Oh, also Dark Side of the Moon. He wasn't freaked out by the dog in Sam's memory.

I'd have to rewatch All Dogs Go To Heaven to see how he treated the skinwalker, but he didn't really interact with the dog in Sam's memory--he just looked at it, right? I've never said he's freaked out by them (and neither did the text, that I see)--just that he doesn't like them, isn't comfort(able/ed) wrt them, certainly not in drawn to them the way that Sam was, and certainly not empathetic in the way he is now.

I thought people/someone had said before his dislike of dogs came from fear, after the hellhounds. Aside from him running from the Yorkie in Yellow Fever (which seemed like just a perfect sight gag), I don't recall him being afraid of dogs at all. Before that, based on Mystery Spot if nothing else, he seemed to like dogs. Then in 8.01 he was suddenly adamant about "no dogs in the car!" which I can't remember ever hearing from him before.

Sam has always clearly seemed to like dogs. Dean, it seems to me, has been all over the map. That's about as far as I want to analyze it, honestly. I already said I know part of it is simply my fanon.

He also ended up pulling a gun on a Yorkie in the season six opener.

Right now I can't point you to why I felt 8.01 was a confirmation and not a revelation, but that was definitely something I felt I'd learnt from watching without trying to rely on the hallucination either.

Don't remember which number "man's best friend with benefits" was but in it the lover/pet/familiar said that she could sense in her dog form that he did not like dogs. Dean denied it... Evidence for ita !'s theory.

I forget the episode, but the two of them had to cross a courtyard and climb steps past a pair of leashed GSDs. Dean went first, hurried, stiff, with a stoic expression of locked-down terror. Sam followed after with squinchy face of askeeredness, moving fast, arms and shoulders pulled in. I read residual fear of hellhounds echoing from proximity to mortal dogs from both of them. Though I admit that may just be me reading in.

Wasn't that the one where one of the Fates had their number, so they were on the lookout for almost anything that could take them out Final Destination-style?