Courtesy of LLM:

Could be the 2003 Disney movie Pirates of the Caribbean: The Curse of the Black Pearl? Not black & white though.

It’s spoken by Captain Hector Barbossa (played by Geoffrey Rush) to Elizabeth Swann (Keira Knightley) during a tense moment on the island. The full exchange is:

Barbossa: "You’re a cruel one, Jack Sparrow. You’ve doomed us all!"Jack Sparrow: "Not all of us."(Elizabeth then shoots Barbossa with a pistol.)Barbossa: "I had to shoot you, darling. It’s nothing personal. You’re just the only person I’ve ever met who is as evil as I am."

Could be the 1940 pirate film "The Sea Hawk", starring Errol Flynn and Claude Rains.

In one scene, the villainous Captain Thorpe (played by Claude Rains) says to the protagonist, Geoffrey Thorpe (Errol Flynn), something along the lines of:

"I had to save you—you're the only man I've ever met who's as big a scoundrel as I am!"

Another possibility is "Captain Blood" (1935), also starring Errol Flynn and Basil Rathbone, where rival pirates exchange similar banter.

Other options are:

• "The Black Swan" (1942) (with Tyrone Power)
• "The Buccaneer" (1938) (with Fredric March)