You shouldn't trivialize actual mental issues people have.
Terry notices that his coworker is counting to five between every action he completes in his work.
Terry wants to address the fact that his coworker isn't getting enough work done, due to the counting behavior.
Terry asks his coworker if he is experiencing any special difficulties in their work, that Terry could help them work around.
Terry approaches his coworker and complains that they are acting completely crazy, and they need to speed up their work.
His coworker explains that he has OCD but is working on finding ways to mitigate it's effect, he is very happy with Terry's offer to help.
The coworker is offended and hurt by Terry's characterization of this behavior, which is not his fault.