The God of the Old Testament is clearly vengeful, tyrannical and jealous.
Christians justify this by saying that a lot of that book is not to be taken literally and/or the commandments were superseded by Jesus' teachings in the New Testament. By doing so they are making their own interpretation of the Bible and hence they are deciding what is right or wrong for themselves like anyone of no faith.
The way I see it is if God literally appeared and judged everyone today, most Christians would be found to be not worshipping him how he asked nor following his law.