Fighting with Gloves on
Sparring without showing animosity; fighting with weapons or words with coloured friendliness. Fighting, like boxers, with boxing gloves. Tories and Whigs in the two Houses of Parliament fight with gloves on, so long as they preserve all the outward amenities of debate, and conceal their hostility to each other by seeming friendliness.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894
More on Fighting with Gloves on from Fact Monster: