Landon Barker Slammed for Diddy Sex Jokes at 21st Birthday Party

Landon Barker is catching some flak online over a recent party ... with commenters blasting him about some Diddy jokes made by others at his 21st birthday party.

Here's the deal ... Landon and his friends celebrated his 21st at Harriet's in West Hollywood ... and eyebrow-raising clips from the celebration have surfaced.

At Harriet's, Landon reportedly ordered bottle service -- and the DJ at the joint sent out servers carrying bottles of baby oil with flashing lights inside ... a clear reference to the federal government's claim more than 1,000 bottles of baby oil were found in raids of Diddy's homes earlier this year.

We're told one of the servers tried to hand Landon a bottle of baby oil, which he refused.

Later on, the DJ at the bash can clearly be heard saying, "We're getting really freaky tonight. We're getting Diddy freaky tonight." Alleged group-sex "Freak-Offs" are at the center of the feds' ongoing case against the music producer.

As you can imagine, people are saying these wisecracks weren't very wise at all.

Neither Travis nor Landon's stepmom, Kourtney Kardashian, were at the party.

As you know ... Diddy was arrested last month on charges of racketeering conspiracy, sex trafficking by force, fraud or coercion, and transportation to engage in prostitution.

He's still locked up at MDC Brooklyn after his requests for bail were shot down by two different judges. At his most recent hearing Thursday, Diddy's new legal dream team asked a judge to expedite the process of feds handing over evidence in the case.