It's not hatred, it's an objective opinion. I worked with APL professionally for about ten years, starting back in the early 80's. I used both mainframes and desktop computers. I was very involved in the community, attended annual conferences, presented a paper in one of them, admired Iverson and some of the other luminaries of the era, I even have a very dorky looking picture of myself with Iverson.
I think that I can say that it is because of this that I was very aware of what was going on with APL in a commercial sense. It was very difficult to evangelize the language when, in the 80's, the friction points to adoption were many --the character set being one of them. It took a major effort on my part to convince a biotech company of the era to adopt APL for analysis of human DNA sequencing data.
All of this to say I believe I fully understand the decision to remove one of the impediments by discarding custom symbols and coming up with whatever could replace them that was present in computers of that era. This meant ASCII characters that could be typed by anyone on any machine. Almost anyone desperate enough to make the language gain a foothold in the market would have considered such a solution.
That was the driving force behind J. Nothing else. I never heard Iverson say "We moved away from notation because this is better". Never. Because it wasn't. It took a wrecking ball to what he had been teaching and talking about for decades, the foundation of his career, really. They needed market (and financial) success and made the wrong choice.
It wasn't long until custom character sets were a non-issue. Anyone who stopped to think about this a bit would have understood that transition was imminent. APL had the same problem that, say, Japanese had. IBM PC's required altered character ROMs and keyboards to be able to use Japanese. If you had to work with both English and Japanese you likely ended-up with a solution similar to early APL, a modified graphics card with a toggle switch mounted in front of the computer to change character sets.
And so the pressure to build computers that could do non-ASCII character sets with ease was there and it was very real. Remember that IBM never thought the PC would go anywhere. The machines only became more than the sum of their parts once mass adoption took place and clones got faster, cheaper and better.
Had Iverson stuck with APL as it was he would have been able to see it flourish on new more capable hardware. By doing what he did with J he likely bifurcated (or more, because there were other pure APL factions already, like IBM APL2) the community and likely contributed to the language languishing.
It only makes me angry in the sense that all of this has caused a situation where modern software engineers will likely never experience what notation can bring to the domain. APL used to be taught at a number of universities. I don't know if any even bothers to mention it yet.