Urlacher -- a Hall of Famer who spent his entire 13-year NFL career with the Bears -- set social media on fire Thursday ... by taking a shot at the NBA boycott.

"Brett Favre played the MNF game the day his dad died, threw 4 TDs in the first half, and was a legend for playing in the face of adversity,” Urlacher's post said.

"NBA players boycott the playoffs because a dude reaching for a knife, wanted on a felony sexual assault warrant, was shot by police."

Urlacher also appeared to "like" a social media post that said, "Free Kyle Rittenhouse,” the 17-year-old who allegedly shot and killed two people who were protesting the shooting of Jacob Blake.

The backlash was fast and furious ... with several high-profile outlets trashing Urlacher.

Isaiah Thomas wrote, "That’s sad smh. He’s a real life sucka for that."

Quentin Richardson added, "And To think I used to cheer for this dude as he played for my Bears!! F*ck outta here Urlacher!! U trippin!"

Ex-Bears running back Matt Forte -- who played with Urlacher -- said, "The comment [Urlacher] posted is void of empathy, compassion, wisdom and coherence. But full of pride and ignorance!"

"I pray for those who have been blinded by their wealth, privilege and earthly fame that breeds arrogance in their hearts."

"And those who refuse to Acknowledge racism and injustice but instead choose to place their energy into justifying it by quickly judging the victims life as if they themselves are more valuable because their sins are different or weren’t caught by man ... but God sees all."

Enter the Bears organization ... which quickly issued a statement on the matter.

"The social media posts in no way reflect the values or opinions of the Chicago Bears organization."