I was under the impression that only the Animal Friendship component of Yuan-Ti Purebloods from Volo's Guide to Monsters was limited to snakes, and Poison Spray + Suggestion could be used as stated. I've run into a DM in organized play who is arguing that Suggestion is limited to snakes only, and I cannot find any official text anywhere clarifying this.
It doesn't make much sense to me that Suggestion would only work on snakes when Suggestion requires the target to understand you. Outside of special circumstances, most snakes would not be able to understand you as a Yuan-Ti... The Animal Friendship part of this ability is the only part that lists this restriction, and it seems to only restrict that spell rather than the entire trait. Otherwise it would also imply Poison Spray could only be cast on snakes, which is just silly from both a canon and utility sense.
The exact wording is as follows:
You know the poison spray cantrip. You can cast animal friendship an unlimited number of times with this trait, but you can target only snakes with it. Starting at 3rd level, you can also cast suggestion with this trait. Once you cast it, you can't do so again until you finish a long rest. Charisma is your spellcasting ability for these spells.
Despite my arguments against it, this DM seems set on his ruling unless I can find something official stating otherwise. Anyone know of any references to this ability I can show him?