I doubt it was intended at all. It was probably a matter of stage framing. Linus gives the prayer so sits at one end of the table. Snoopy serves the food and should be at the other head of the table but for framing had to be next to peppermint patty to show her disgust as he serves. So they both sit together. Charlie Brown has to be next to peppermint patty so she can argue with him in camera frame about what blockhead served the food. That leaves Franklin, Marcy and Sally to seat. Sally sits next to Charlie Brown, she’s his sister after all and… Marcy gets the other head of the table (technically alone) and Franklin gets the other side to balance out the scene.

It’s a complete non-event and they only screamed racism because they needed something else for the daily outrage session!