If you read the Quran you'll find that it is much like the Bible and there are definitely peaceful Christians. Where Islam differs is in The Hadith or 'sayings of the Prophet' which aim to help people live a good life and interpret the Quran correctly. Which Hadiths are accepted, questioned and rejected depends on the sect of Islam (Sunnis and Shias have different Hadiths) and the different schools of Islam. Whilst there is some commonality in the stories there are also differences and with these differences people can interpret, for example some Muslims believe most music is forbidden whilst others say that it is not. Where there is interpretation there is room for Islam to be both a religion of peace and equality and a religion that is aggressive and oppressive. One of the main teachings of Mohammad is God's forgiveness. Much like in Christianity Muslims believe that God will forgive any sin if the sinner prays and repents, as such many Muslims don't believe is harsh laws and punishments but rather gentle guidance. The problem with Islam is the ability to find a Hadith for everything, because they are sayings only some Hadiths are taken as fact, there are many more poorly sourced sayings (ie. My brothers wife said that her mother once heard Muhammad did such and such). If a person wants to they can probably find a poorly sourced Hadith to justify most actions and many people will listen to them believing that they are following a path to Heaven.