To bring this back on track...
1) the fact the store told your friend to get an i7-3770k for gaming says all you need to know.
-The i7-3770k benches and games identically to an i5-3570k, or even (when everyone is overclocked) an i5-2500k. Hyperthreading does not help when gaming. so whatever advantage the i7 might have in multithreaded tasks is null and void. Since you pay an extra $100+ dollars for that i7, i think we all know what the motives of the store people are.
2) the only reason a merchant of any type would say Product X is junk, is if they didn't carry Product X. Most merchants on hearing your friend was there to look at an AMD FX 8350, would say "sure, come right this way." in hopes to sell a computer. The store that doesn't have any AMD computers on the other hand will say "you don't want one of those, they're junk." Again, in the hopes of selling him a computer. If they say "we don't have one, he'll walk out the door, if they say "you don't want that, this is better" they might sell a PC. simple sales techniques my friend.
3) Your advice with the FX 8350 was a little flawed in the first place. If your friend's main goal was gaming, not $$ or several of the unique uses an AMD is better then an Intel, then you should have pointed him at an i5-3570k. They're so close to the same price as to make no difference... and while there will be a few games where an AMD will be better, and a few tasks/aps/situations where the AMD will be better, generally the Intel will outperform the AMD by a little bit. Better advice would have been an FX-8320; as at that price point, intel has no answer, and it overclocks as well as the fx8350 (its an undervolted 8350, as it's not binned, for $30 less). By going for the flagship you opened up the performance debate, and now, i fear nothing you tell your friend will work anymore. You've lost credibility i think, and he'll doubt whatever you have to say about pcs from now on. especially since all he needs to do is google search fx8350 vs i5-3570k.
4) be honest with him about the issue. Be honest about the store and their unknowledgeable advice, and be honest about your own bad advice.
5) as to the heart of his question, is AMD junk chips? No... I've used AMD for 2 decades now (on an intel at the moment so i've used both)... and i've NEVER had a CPU fail. Dozens of CPUs, dozens of pcs build, for friends and myself, and never once has a cpu been bad. I've had bad ram, hard drives, gpus, motherboards and psus... never once a bad cpu. Its a joke argument. You'll notice if you check around there are no articles about junky CPUs... it's a stupid argument made by a salesman trying to sell a pc. Not a knowledgeable one.