It's a complex issue but one that needs to be confronted head on.
All religions are old belief systems and naturally reflect their age. All religions need to change to keep up with changing times and advances in human civilization.
There's no way that one can cling on to ways of life propounded in texts written thousands of years ago — no matter how suited those ways of life might have been to the times and climes they were written in.
Let's face it: religions came into being as humans tried to make sense of a perplexing universe. There was no science then. So, religions provided simplistic explanations for natural phenomena. Pretty much all religions have concepts of heaven and hell. They talk about living a pious or righteous life here on Earth so that one gets to go to heaven in the afterlife instead of getting punishment in hell for eternity.
This is certainly as silly as it sounds. I don't know how people can believe in childish stuff such as this.
Beyond this, different religions have different idiosyncrasies. The problem with evangelical religions is that they proselytize. The problem with expansionist religions is that they believe in going to battle to fight for their religions. The particular problem as I see it with the religion that I was born to — Hinduism — is that it has got rather peculiar practices of worshipping idols which is unique to this religion only. Nothing wrong perhaps with worshipping gods who might have four heads or ten hands — it's just silly as hell!!!
If some religion proclaims that all those people who don't follow that particular religion are infidels and must be either converted or killed, well, that's dangerous. People must stop believing such nonsense and must not be and cannot be allowed to act upon such nonsensical beliefs. It would appear some sections of the Muslim world believe in this. May be this is not unique to Islam. But because of various historical circumstances, Muslims feel victimized and have reacted to that sense of victimization by resorting to violence.
It's a basic, inconvenient fact that 19 or 20 people decided to fly airplanes into buildings and managed to kill about 3,000 people. They had lots of help and they had lots of grouses. And they want to kill even more people. This is pure madness. People continue to kill almost everyday using the almost invincible method of suicide bombing. Another monstrous caricature of religions teachings.
Be it on the record that other beliefs have prompted nations to commit murder and slaughter on far larger scales. Let us not forget the brutal history of the Second and First World Wars. Killing civilians or soldiers in the millions cannot be redeemed by any explanations. Nuclear weapons are not less brutal ways then using suicide bombings. Fire bombings, gas chambers, napalm, machine guns, etc. — each one is equally bad.
The nationalistic pride and notions of racial superiority which led to such barbarity for centuries has hopefully come to an end.
The religious zealotry of a few fanatics can hopefully be dealt with in this century using a combination of education and opportunities for self-growth.