"Because I don't want to." would be more frank and straightforward than all those made up arguments.
"I'm unable or unwilling to read." would be more frank and straightforward than this summary.
It's due the reasons I covered in "all those made up arguments", as you call them.
What do you really expect to gain business-wise by publicizing a misguided personal grudge with a poorly written post? You don't mention you live in Taiwan. You don't even mention that you give discounts to non-US universities. So, in the end, you come out no better than those "other" companies. The post doesn't work as a publicity stunt either, as you make no mention of the product you're selling.
Why not opaquely offer e.g. a 10% discount to .edu emails and a %40 discount to less-"privileged" universities. No explanations needed, you just receive a discount code in your email address. No drama, no grudges, no need to write lengthy posts and argue with strangers on HN.
Disclosure: Never had a .edu email.