Mourinho has only been in charge since November, but ahead of victory over Everton he was under pressure.
"That's just the world we live in nowadays," Dier told beIN Sports. "I think it's kind of crazy. We've been together a very short period of time. We've gone through circumstances which no one could foresee.
"The change of manager half way through the season, followed by many, many injuries and then the coronavirus pandemic.
"There have been many obstacles to overcome and we hope that those things will bring us closer together.
“Those kind of comments are just ridiculous really."