people are fully within their rights to state their opinion
Doesn't good manners come into this?
"Good manners" (which are a cultural construct) by what standards? Be aware this isn't a British forum, this is a forum with a truly global audience, with various cultures which all have slightly different opinions what make "good manners" (for example some cultures are more direct and it's considered polite to say what you think and being frank, while another may present a superficial but excessive politeness just to stab you in the back when you turn around).
""Those prices are far too high for me" is one thing and "You have no idea how to run a business" is just armchair warrior speak. Would you say any of this stuff to someone's face? If not, it has no place here either."
Besides these "quotes" are pretty much your interpretation (probably because you are already pre-opinioned), to answer your question: no, I wouldn't have problems giving my observations face to face. BTDT many times.
And frankly, if you really have hesitations telling a vendor if a price is too high for you then you should probably seek professional counselling. Seriously.
why are you even reading this thread if you don't like it
Perhaps because there was some interest in a possible deal. Which is less likely to happen as the aggressive, verging on spiteful, attacks increase.
So what stops you making a deal then? I guess the vendor will gladly sell you these items for the listed price, irrespective of the comments.
But I would suggest, instead of falling into silly hyperbole, you should spend a moment considering that not everyone asking questions or commenting on pricing is out to "get them", in fact you should seriously consider that maybe there are objective reasons for questioning the offer. For example, anyone who even knows the faintest bits about the T&M market knows that the offered discounts are ridiculously low (that's a given). Or that someone who acually has run and coached businesses may have a better understanding how precarious many smaller businesses operate, and with reason becomes a bit wary when a vendor publicly comments of affordability of what at the end are already miniscule discounts. Which, as stated before, is very relevant when your warranty depends on the vendor being in business throughout the warranty period. Or that there's a difference between a "refurbished" product and an used one, which means claiming a used piece of kit has been refurbished when it hasn't is fraud.
In short, you should always consider that your simplistic explanation of "aggression" and "spitefulness" may be wrong, that things are a bit more complicated than you imagine, and that maybe there are things you just don't know. And considering that I'm not the only one criticizing the offer, there's also the old saying "no smoke without fire".