You may not have made the right choice, but it's not because you chose ASP.Net over PHP (you'd probably be asking the same question if you picked PHP). It's because (and I'm sorry if I'm being too blunt) you didn't seem to question what you were doing or go out and seek alternatives. You mention the "drag and drop" world, but that's not the only way to implement those features. We both worked in the same world at the same time, but I didn't like the "magic" the drag and drop functionality provided. It didn't give me enough control over what I wanted to do so I figured out how to do it manually.
My response is a bit more rambling than I intended for it to be and I hope you can piece it together. :) My main point is that we both ended up with the same choice (ASP and ASP.Net) around the same time but I also have those bullet points you mention checked off. I don't regret my decision one bit and I don't think it has stunted my professional growth at all. If anything it has probably helped it because .Net devs are in high demand and highly paid in my area.
Edit: Hah, I wrote this post without knowing who you are at all. I may very well be wrong, but that was the impression I got from your comment and the original article.
These were choices made by my contracts and my employers. What you're saying is valid: I could have pushed to use another system or platform. I can do this now - but back then it was not nearly as easy to just pick up and learn the intricacies of different platforms. You might disagree, it's sort of subjective - but installing PHP/MySQL was a complicated affair if you're not familiar.
Finally - the whole premise of the post was the very question itself: "Did I do the right thing?". I was questioning, and I had to make a choice. I constantly did (and still do) that.
His affinity for everything non-.net and the effort he puts into helping keep feedback loops going between platforms while focusing on surfacing the better patterns, overall, is pretty admirable. His religion seems software dev, not platforms.
He might get acerbic to some, but it seems part and parcel to his personality. He's not content with friction, ceremony, and negatively reinforcing paradigms. The final output from this is most often quite beneficial. If for nothing else, I appreciate that he spends the time doing the things that I would do if I hadn't yet sold any of my start-ups.
I'd only suggest, in this case, that one can be better off carrying awareness of the time wasted in suffering. You may well waste less time going forward with the lessons learned. You will waste less time and suffer less prospectively. Hopefully you haven't missed the last plane off the island... in Hawaii... where it's not so bad to be stuck...