It will always return to this with Islam.  If not the 1984 Israeli murders in the Olympics, if not the 1993 attempt to bomb the World Trade Center, if not a copilot of a 747 yelling "Allah Akbar" as he drove that jet into the sea, if not the 2001 atrocities, if not the beheadings, if not a "Soldier of Allah" killing at Ft. Hood, Texas, if not yet another "Muslim convert" beheading a woman in Oklahoma, if not ISIS.....

Over and over and over.  This becomes the theme, the central narrative of Islam.  

I don't HATE Islam, but in the absence of strong and near unanimous FATWAs from the religious leaders against these barbarians in their midst, I cannot respect it one bit.   It is unworthy of respect.  Does not matter if some believe it is good, the best, the word of god, blah blah blah.

Certainly many consider that these minority violent fragments of Islam are quietly and passively tolerated by the greater societies of Islam, and are often funded under the table by many who would not openly admit it.  

Evidence points in that direction.  We know many in Saudi Arabian supported the 911 hijackers, we know Pakistanis celebrated with street parties at 911, we know that ISIS and many other violent groups are supported monetarily by other Muslims.

The historical evidence does not show that the Muslim religion contains sufficient clarity to adequately safeguard against what you call "deviant teachings."  That is I think what others on this thread have been trying to explain to you.  The books themselves can and do support the "deviant teachings".

To adequately comprehend the problem, it is best that a Muslim discuss such a matter with reasonably knowledgeable non-Muslims, whether they be Christian or atheist or something else.  In many cases they will be far less biased than your own mullahs and such and will see things clearly.