This line comes after Algie's explanation of Bunburyism, his use of a fictional friend to escape social situations. Jack, although he has a similar false brother to use for escaping, believes that Algie's actions are immoral, and claims that he will have no need of the fictional person once he marries. Algie comments that "in marriage, three is company and two is none," and when Jack rebuffs the statement as a product of French moral corruption, Algie makes the following claim:
Algernon: Yes; and that the happy English home has proved in half the time.
Jack: For heaven’s sake, don't try to be cynical. It's perfectly easy to be cynical.
Algernon: My dear fellow, it isn't easy to be anything nowadays. There's such a lot of beastly competition about.
(Wilde, The Importance of Being Earnest, gutenberg.org)
Jack, still caught up in the optimism and euphoria of love, believes that marriage will solve all problems, leaving no need for white lies such as Bunbury. Algie believes that marriage is a social contract like any other and that married people need to escape sometimes, and that Bunbury is harmless. Jack believes that Algie's cynicism is an easy solution to the complexity of life's issues, and that he is being lazy to avoid commitment and responsibility. Algie, however, believes that most people are already cynical and so it is necessary to work hard to avoid the tricks and white lies performed by others. This shows how Algie is using his intelligence to avoid responsibility, while Jack is still naive enough to believe that love conquers all.