A graphics card is a versatile tool. This tool can be used for games, accelerating work (rendering, Photoshop), hobbies (distributed computing), and making money (mining), etc. Picking on one particular group that buys videocards for their purpose and ignoring another (i.e., how someone else might buy 100 videocards for a university computing project) is ignorance at its finest.
Miners are not to blame here at all. The blame is on AMD/GloFo. AMD released a tool that can perform tasks A, B, C, D, and the demand for task/workload D has exacerbated shortages. AMD failed to build up inventory in anticipation of rising market demand, despite having full awareness there was going to be very large demand from customers with workload D. Whose fault is it when a company fails to meet supply? Not the customer's fault.
I can just as easily claim that gamers are cancer to PC gaming because I cannot buy a GTX1080 farm for Blender. Sorry, no. GTX1080 is out of stock because there is large demand for workload A, but once again it's NV's/TSMC's fault.
The OP's argument fails to separate the fraction of PC gamers buying cards for gaming vs. mining, and yet puts the entire blame on miners. There are plenty of people online mining alternative coins on NV and AMD cards, and also many more buying these products for other workloads such as games or distributed computing. Without having the data which shows the % of miners vs. customers who buy GPUs for other uses, we cannot discount that RX 480/1080/1060 videocards would have sold out to gamers alone even if miners weren't interested in the cards.
Moral of the story: it doesn't matter why the videocard is in demand and what workload the consumer runs on it. It's the manufacturer's job to meet demand, not the consumer's job to buy just 1.
Considering AMD publicly stated that 84% of the PC gaming market buys GPUs between $100-300, and they aimed RX 480 squarely at that bracket, they wouldn't have been able to meet demand for months anyway because there are about 10 million dGPUs sold a quarter. Miners are a tiny fraction of 10 million quarterly GPU buyers. The total Ethereum network rate is about 4 million MH. If the average AMD GPU mines at 20-25MH/sec, that's only 160,000-200,000 cards; and the network rate was almost 4 million before RX 480 even launched!!
It's impossible to blame miners on the shortages of RX 480 if AMD was serious to claim they were targeting 80%+ of 10+ million customers a quarter.