Jürgen Hubert
First Post
I really don't see the point in this artificial divide between politically correct reptilians, and "kill on sight" reptilians.
Personally, I'd say the dividing line between "PC races" and "NPC races" is:
"Can we sell stuff to them/buy stuff from them without getting killed/eaten?"
If the answer is yes, they count as "civilized" and likely won't be attacked on sight in most except truly xenophobic settlements. If no, eventually one side will attempt to kill the other.
The "implied backstory" says that in the last human empire, all the PC races managed to live together, and this created a certain measure of trust that still endures to this day. For a good metaphor, think back to the time of the Roman Empire. The Greeks disliked the Romans, who in turn sneered at the Gauls, but ultimately they were all members of the Roman empire and theoretically received some measure of protection by it. In contrast, all of these were deeply suspicious of the barbaric Germanic tribes to the north, and any trade and other contact with them was rare and only happened at a few places.
So let's say the human empire of the backstory managed to conquer a good chunk of the world - halfling marshlands, elven and eladrin forest kingdoms, dwarven mountain strongholds, and so forth. They convinced dragonborn nomads to join their armies (where they probably joined certain elite units), and tieflings had always dwelled in communities in their midst - widely distrusted, but with abilities that were too useful to ignore. And everyone learned Common and learned to communicate with each other.
On the other hand, there were some races which the Empire never conquered and assimilated before it collapsed. Orcs were too fierce to submit to civilization. Others, like lizardfolkn, simply dwelled in regions too far away. As a result, they never learned Common in large numbers, were hard to trade with, and didn't leave their native regions in numbers large enough to be accepted as "civilized". Ancient manuscripts from the Empire talked about the "civilized races" - the PC races listed in the PHB - but the lizardfolk were never more than curiosities, complete with the kind of stories authors like to make up about foreign countries to send a chill down the spine of their readers and make them glad that they live in a civilized region.
Of course, it's perfectly acceptable that lizardfolk are counted among the "civilized" races in your campaign world. But if you want a justification for the current setup, here it is...