Rofl! I hear you. Riccky definately hears you!
No need to clarify your thoughts for my benefit, I understand perfectly, I just dont care!
Riccky in fairness, one day ,one may simple freak at the other and attack it savagely infront of your customer, dude,
not a great way to sell an animal. Just be a little careful maybe. It was more the size difference than the species difference that alarmed me, even though I said nothing. Post a pic of a dead or seriously mangled cham on that counter, and your on your own.
You might beleive you can predict what the lizards will do, but do they know that?
You took a snapshot of, and shared with us, a unique look at the behaviour of two different species of chameleon interacting,
If Sir David Attenborough did that for a new documentary, Id still watch it! I found it fascinating and enjoyed thinking about how they might've behaved, had they been alone and left to their own devices.
That said, its been made clear this is not something thats a good idea to do on a regular basis. But,
thats no reason you cant display two different species for a customers comparison. Maybe you could rig up the counter in such a way that you could display both, but a few feet from each other.
Then they can still compare, the chams cant fight and worst (or best, depending how you look at it) that you will get, is males showing territorial /dominance /threat/defensive displays.
How often you do that, and weather continued natural stress like that effects the animals health, is another matter.
The vendor needs to be a good example in husbandry at all times IMO, cause this is where the people who don't know any better get their pets, and info. 
