Lindsey Graham is no Jack Osbourne when it comes to the intersection of celebrity and politics, telling TMZ DC ... celebs should absolutely use their platforms to get involved, even if they're gonna be "obnoxious" about it.

Charlie got the Senator from South Carolina on Capitol Hill and asked him about a comment Jack made to us last week ... namely, that celebrities should "shut the f*** up" when it comes to politics.

Lindsey couldn't disagree more.

The way he sees it ... people fought and died for Americans to have the freedom to speak their minds about all issues -- including politics -- and that includes famous citizens.

Some folks think celebrity political musings or endorsements aren't worth diddly -- arguably, they didn't help Kamala Harris -- but Lindsey explains why that's not always the case.

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Basically, Sen. Graham's saying everyone is entitled to their own opinions and should feel free to express them ... whether that's Jack or Chelsea Handler, who had a lot to say about Spencer Pratt going from reality TV to the thick of the Los Angeles mayoral race.

Check out the clip ... Lindsey says shutting up one section of society is a slippery slope.