Jabba,
The Quran does ordain the amputation of the right hand as the ultimate punishment for theft - but it is the last resort, and as this is how it has as is being carried out, I would imagine this is how it is being taught as well.
As for the killing of Gays - yes, there are many muslims who believe this to be the punishment. Similarly many muslims are taught and believe that the punishment for apostacy (leaving/renouncing Islam) is death. Both of these are incorrect from a Quranic and Sunnah (the practice of the Holy Prophet, pbuh) standpoint.
In my view, Islam is going through the equivalent of the Christian Middle Ages where the Mullahs are doing what the Church/Priesthood did in the Middle Ages - using Islam for political means and twisting the meanings and teachings for their own ends.
The fact that the self-same 'teachers' will not encourage people to read, question and think is a great clue about their insecurity. The rejection of science and things modern is an insult to the many great Imams and scholars of Islam in the past who revelled in the study of the sciences.
But don't get me wrong - the Mullahs are just doing what is in their self-interest and as history has shown, blood-lust against a foe is a great (and more to the point, distracting) rallying call. These issues are really at the periphery of Islam and 99.9% of the time have no relevance to the lives of a believer - Muslims aren't going round gay-bashing or looking to execute anyone who stops being a Muslim - they are busy leading their own lives - as is everyone else.
Cheers,
Shafique