Lavigne came to the defense of Kroeger and his band Nickelback on Thursday after Facebook co-founder Mark Zuckerberg made a joke at the band's expense.
The diss came in a YouTube video shared on Tuesday, in which Zuckerberg promotes his home artificial intelligence assistant Jarvis (voiced by Morgan Freeman).
While demonstrating how the A.I. system can help with everyday tasks around the house, Zuckerberg asks Jarvis to play "some good Nickelback songs."
"I'm sorry, Mark. I'm afraid I can't do that," Jarvis answers. "There are no good Nickelback songs."
"Good. That was actually a test," Zuckerberg responds. "How about just play some songs that our whole family likes."
The tongue-in-cheek comment did not sit well with Lavigne, prompting a visceral takedown addressed to "Mark."
"Many people use your products -- some people love them and some people don't. Either way, you're allowed your musical opinion however, your jab at Nickelback is in poor taste," Lavigne tweeted Thursday. "When you have a voice like yours, you may want to consider being more responsible with promoting bullying, especially given what's going on in the world today. #SayNoToBullying #TheJokeIsOld #NickelbackHasSoldOver50MillionAlbums."
While Lavigne and Kroeger have been separated for more than a year, the two have remained friends. A month after announcing their separation in September 2015, the two were snapped working on new music together in a recording studio.
Photos popped up of the former couple cuddled up at Clive Davis' Pre-GRAMMY Gala in February, and they were back in the studio again in March.
Lavigne and Kroeger first began dating in 2012 while working together on her fifth album. The pair wed on July 1, 2013, in the South of France. They have never officially divorced.