Harrington sent off Andrew Robertson on 18 minutes for blocking Harry Wilson from a goalscoring opportunity.
"I had some conversations with the players of Fulham, and we felt that the referee was nervous," Van Dijk told Sky Sports.
“I felt he couldn't really communicate normally with Robertson. We're all talking about protecting the referee, but I couldn't talk to him. But we shouldn't make it too big because this is not the reason we left points.
“It is the way it is. We take this point with us, recover quickly and make sure we are ready for Wednesday."
- Get breaking football news faster with the new Tribal Football app! Download now on iOS and Android to stay ahead of all the latest transfers and football updates. Download now: App Store, Google Play