So everyone asking "Why didn't we arrest and deport Tamerlan Tsarnaev two years ago?" needs to understand at that point he hadn't committed any crimes, and you need to just sit down and shut the hell up.

The FBI admitted Friday they interviewed the now-deceased Boston Marathon bombing suspect Tamerlan Tsarnaev two years ago and failed to find any incriminating information about him.

As first reported by CBS News correspondent Bob Orr, the FBI interviewed Tsarnaev, the elder brother of at-large bombing suspect Dzhokhar A. Tsarnaev, at the request of a foreign government to see if he had any extremist ties, but failed to find any linkage.

Both Tsarnaev brothers were legal permanent residents of the U.S. There is no evidence so far that either brother received any tactical training.

CBS News correspondent John Miller reports it is likely Russia asked to have the elder Tsarnaev vetted because of suspected ties to Chechen extremists.

The FBI is likely to have run a background check, running his name through all the relevant databases, including those of other agencies, checking on his communications and all of his overseas travel. Miller reports that culminated in a sit-down interview where they probably asked him a lot of questions about his life, his contacts, his surroundings. All of this was then written in a report and sent it to the requesting government.
The guy was clean then.  If it turns out later that more evidence is out there to the contrary, then we'll take a look at it then.  But in 2011 this guy got paid a visit.  What happened between then and now, I can't tell you.

Rampant speculation on the other hand, without the fact?  Zero percent of that helping anyone.