I hate the word "dated", because it can only sensibly apply to a work in which the characters or plot don't reflect the era.
So, actually, what most of the internet educated IMDb users claim to be "dated" are often the only films not "dated". "Dated" means watching a movie about Wyatt Earp, and getting the feeling he has played video games instead of thinking about local events.
Here, we have a film that is definitely not dated. It deals with a handsome Communist spy who has to work his dealings around his personal life.
Robert Taylor's character is very credible, and multi dimensional. If this movie was made by one of the beavis and buttheads of today, he'd simply kill everyone who coughed when he told a lie. Yes, you're right. This would mean the world population would be zero humans within a month, and it makes no sense.
Here, in "Conspirator", he is a real person, and so is his wife, who is onto him. In dramatic style, they still want to work their relationship, and honestly, this is what people do, when they find something out about each other. Real people don't murder each other each time they find out a secret about each other.
We're shown early that the pace of the film skips over minor details, which modern writers deem so important. In one sense, some would say that "dates" this film, since it is more plot oriented, more Shakespeare than Tennessee Williams. Intricacies aren't explored as much. We're given the story line and the story, and the length of the movie allows for that.
Is it completely perfect? I don't think so. However, the characters are more credible for the time than people today can handle, so it probably isn't safe to show friends. People will have a problem with the iconoclastic attitude towards today's "everyone is a psychotic killer" philosophy.
