The Two Faces of God

I have a problem with the Bible. 
To put it simply, I don't understand why the old testament and the new testament are linked together in one book since we are talking about two entirely different gods. 
 I mean, we don't add the Quran as a third book to the Bible- do we? So why do Christians insist on holding on to that old, psychotic, narcissistic, vengeful, hateful, megalomaniac ''god'' describe in the old testament as if he were their own?
  The two are completely different entities. 
 Let's review the two of them, see if they're anything alike.
  The old one hates Humanity so much, he's not above drowning them all- including the innocent and the unaware- in a fit of rage. And yes, that includes newborn babies, their mother and anyone who lived too far away to ''get the news''. 
 Eternal damnation in Hell, for the slightest offense, is his thing. That's bad enough already but that old psychotic goes even further. Your mortal life is really quite insignificant when compared to eternity. One would assume that a *loving* god would allow you every chance you have during that very small window to make amends, repent and do better. But not this one. This one will *hasten* a sinner's earthly demise and subsequent  trip to eternal Hell by turning you into a pillar of salt!
 To this one, slavery is not a problem. Nor is killing someone in your village for planting two different kinds of seeds side by side, or wearing fibers made of two different threads or stoning an unruly child to death at the village gates. Or throwing gays and lesbians off of rooftops (they're an abomination, he says). 
 And the bastard just *loves* to torment you. ''Kill you firstborn in my honor!'' he commanded to what's-his-name, just to test him but the poor fucker didn't *know* that!
 Imagine that poor guy's dilemma. Go against the expressed wish of that crazy-ass, vengeful, quick-to-hasten-your-demise, irritable god or slay your kid!
 Oh yeah! I FEEL the love!
 Now take the other one, the New Testament one. The Christian one. 
 Loves Humanity so much he makes part of Himself mortal and offers it to His children to wash away all their past transgressions (sins) while providing a bridge to eternal salvation for all the ones to come. 
 Through His son, He admonishes tolerance, abnegation, charity, forgiveness and PEACE (turn the other cheek, do not throw the first stone, etc...) Whereas the old megalomaniac sought to rule every darn aspect of mortal life, this one tell us His kingdom in not of this Earth and that you should render to Cesar what is Cesar's (respect human laws)
 He respects, loves and forgives whores (no rooftop one-way ticket for them or any other sexually impertinent creatures); He feeds the hungry, *extends* mortal life by resurrecting the dead, demonstrates His might and infinite powers through *miracles*, not through vengeful plagues, mass murder or curses!
    And He never tests you, never toys with you or orders impossible conundrums that will twist your moral bowels inside out and leave you shaking with fear or disgust no matter what you decide. 
 The new one doesn't do that. That's not what He's all about. 
 Now, I'm not a believer per se. But if I were *ever* to become one, the only divine entity I could get behind is the Christian god. 
 Not the sadistic, vengeful, hateful, self-absorbed, totalitarian and *unloving* one described in the Old Testament. 
 Why on Earth are Christians still clinging to that old fart is beyond me.  
 But as long as they keep quoting him when they need to forget the new one, they'll find me, right there on the wall, reminding them what I just told here. 
 One is mass-murderer, psychotic fuck. 
 The other one is Love.