Yes, racism is bad. Yes, segregation is bad. Is it particularly relevant in the realm of Foyle's War? Not really. There was a whole lot of moralizing in "Killing Time," and it really bogged down the episode for the first half. Like all countries with large minority populations, the United States had plenty of racial tension and de facto racism in large parts of the country. There were no British blacks in the episode to contrast, so I didn't see the relevance at all.
The murder investigation didn't even get started until two-thirds through the episode, because that's when the murder happened, it was wrapped up rather quickly in the final act. Next week's episode will probably be the final episode of the show, so I hope it's better.
Score: 8.6/10