The cleric from the San Bernardino mosque where Farook worshipped may very well have been related to the terrorist attacks. The cleric was found to have kept in continuous contact with Syed Rizwan Farook in the months before the terrorist attacks. They allegedly exchanged 38 text messages during that time period.
Terrorism accusations should not be made lightly. If there really is a connection it will come to light in cold, hard facts. Anything other than that is purely speculation, and unnecessary. It is important to follow evidence and research things before pointing fingers. Also it is good to assume that people are innocent until proven guilty.
It's not outside the realm of possibility that the cleric from Syed Rizwan Farook's mosque knew something about the attack he was planning, but it is not likely. And such claims are not supported by evidence. We need to move away from viewing everyone who worships at a mosque as being a terrorist. This is not the case, and until we gather more evidence, suspecting them is extremely racist and unfair.
It is mindless to blame one person for the tasks of others that happened to be associated with them. It's this sort of fear-mongering that gets us in trouble in the first place, and that distracts from the real problem. It's lazy, and it's cruel to look for easy targets or excuses so we can feel better about ourselves.