That being said, the grocery prices average cheaper than Safeway by about $10/week for my household (even better since we actually use Uber to get groceries home for large shipments) and we pay $6/week for delivery so Fresh by itself is a no brainer. They have better selection in a few product areas (though way worse in others) so we can combine grocery + grocery delivery to end up with way more options overall.
One of the sad points here is that savings become less available to lower income people as upfront costs price them out of discounts.. credit cards are a classic example, and now things like this.
There is a big difference between the people who are saying "wait, now it costs this much money? ok, I'm no longer buying this: that is way too much for too little value; there's no way I'd pay more than $X (where X might be 0)... I wonder what Amazon might be thinking here" and the people who are leaning on "it is morally wrong to be charging a fee for something that was free yesterday" (especially given the system-wide workaround these people often don't even notice, which is the company with the too-low pricing goes out of business and gets replaced by a competitor that charged the right amount from the first day of operation) or the people who are pushing at "I am incredibly angry at Amazon for doing this" (seriously? there's no good reason to be angry). I do not think the latter two are appropriate behaviors for consumers, and it is those kinds of responses I think the people you are trying to speak at are taking issue with.
I believe the other reply by derefr says more or less the same thing but with more thinking behind why it happens. Meanwhile, I'm saying that I have become desensitized to the sensationalism of social media, tweets in particular, though I still recognize the hyperbole and would prefer less of it.
It helped a lot when I was stuck at home with my newborn but after that I stopped using it as much. I do like the idea of not having to go to the market but Amazon hasn't nailed it yet.
That said, I can understand offended customers taking to Twitter to express their frustration. Sometimes, it's not quite enough of a signal to simply not renew a subscription. If you want the company to actually understand why you didn't renew and possibly improve in ways that matter to you as a customer, you must communicate your displeasure in some way. These tweets are just a convenient way to be heard. And lo, here is an article republishing them, possibly to Amazon's frustration.
I love the free market, and recognize that consumer demand is a very strong signal, ultimately the most important signal for a supplier. But I don't see why consumers shouldn't augment that signal with plain old English.