You can't tell a rock to split, you have to hit it with a hammer, try that.
Tell him this...
The caveat of using a cheap Chinese retailer, whose product is just as good as anybody else's, is that invariably their support is not as good.
You have to buy from Hobbyking under the initial expectation that if you do get a dud, you are gonna have to eat it (by the way if you get a dead cell in a 3s, you can always turn it into a 2s easily). However, the batteries are so much cheaper, that if you get one dud every 5 ordered, you are still WAAAAAY up on your costs if you'd bought all venom.
It's about expectations. Tell him aout the GensAce at hobbypartz as well, they are as good as the nanos according to certain youtube celebrities.