Ralfy the Plug -- DTR's sibling -- tells TMZ ... "On behalf of Drakeo The Ruler, Ketchy The Great and The Stinc Team, it comes off as a spit in the face disregarding the facts that we’ve created an entire movement that generated the momentum for underground emerging L.A. artists to have a platform."

Ketchy, another rapper who was affiliated with Drakeo, also died in 2021 -- and he too wasn't mentioned in the In Memoriam slideshow. Granted, he wasn't nearly as famous.

In any case, Ralfy continues with this barb about cops and free speech ... "Let alone the reality that we lost my Brother, Drakeo The Ruler, the poster child for systematic prejudices against rappers by law enforcement using lyrics against our culture and violating what they call our constitutional rights of freedom of speech- The First Amendment."

Ralfy also notes Drakeo was slain while doing what he loved most ... performing his music. He was stabbed in the neck when he was backstage at an L.A. music festival. The attacker is still on the loose.

He ends by saying, "Leaving Drakeo out of their tribute and by not giving him any acknowledgment of his existence sums up exactly what we feel the industry has been trying to do. Erase us."

Ralfy also says he and the fam appreciate all the love and support they've gotten from the rest of the community ... and promises to keep the truth alive. As you know, Ralfy actually sued the concert promoters for whom Drakeo was working the night he was stabbed.