In the 77th minute at Anfield, with the home team 2-0 up, thousands of supporters left their seats and headed for the exits in a pre-planned walkout to highlight discontent over the club's ticket plans.
Development coach Lijnders, among those taking charge of first-team duties while manager Juergen Klopp was undergoing an appendix operation, watched ninth-placed Liverpool concede twice in the last eight minutes after the walkout.
Goals from Roberto Firmino and Adam Lallana had put Liverpool in control before Adam Johnson and Jermain Defoe replied for relegation-haunted Sunderland.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
"We have one of the best supporter groups in the world ... and if they want to make a statement they have all the right to make a statement," Lijnders told reporters.
"Of course it didn't affect the players. It probably changed the atmosphere in the stadium but not the mentality of the players."
Supporters' groups had urged fans to walk out, the 77th minute being symbolic of the 77 pounds ($111) top tickets on offer for the new main stand next season, a price widely considered to be unacceptably high.
Fans sang the club anthem "you'll never walk alone" before chanting that "enough is enough".
Liverpool chief executive Ian Ayre, though, has staunchly defended the pricing structure.
($1 = 0.6897 pounds)
(Reporting by Ian Chadband; Editing by Tony Jimenez)
