It’s complicated, and no, we shouldn’t discredit religion.
Yes, religious movements have been associated with violent periods in history. However, so have secular, nationalist governments.
It was only recently (post-enlightenment) that the idea of separation of church and state really became an accepted idea. Pretty much all governments pre-Enlightenment era have been associated with religion in some way, shape, or form. Thus, when a particular government or feudal lord decides to wage war on a neighboring state or feudal lord, it will rally the troops using whatever means necessary, including religion, to get people to fight for them.
It is difficult to isolate religion from other socio/political/economic motives that drive organizations to violence. Thus, it’s unfair to say that religion is inherently violent and has been a primary driver of historical violence.
Regardless, it shouldn’t deter us from seeking what is best from ancient wisdom traditions, including religion, and applying it to our own lives.
For a good analysis of the history of religious violence, read Karen Armstrong’s Fields of Blood: Religion and History of Violence.