Luther was very clear to the support of Bigamy as well. And he used Scripture to support this odd view. Ditto the death and destruction of Jews.
You are correct in that Luther supported bigamy -- once. You no doubt are aware that Luther once told a Margrave to marry a mistress whom the Margrave had impregnated. The Margrave was severely distraught, and nothing Luther could say would ease his conscience and ensure that he was still loved by Jesus Christ. It seems that the Margrave thought that because of what the Catholic Church had taught him, he had to do something to make his sin of adultery go away. The Margrave believed that faith alone was sufficient for Christ grace, but he was still troubled. Luther realized that the false doctrine he had fell prey to was the cause, so he said it was best to marry the mistress to clear his conscience.
Luther was a master at working with people regardless of where they were in their spiritual walk with Christ. He took people as they were and brought them closer to Christ.
Until Ambrose derived from scripture that a family consisted of one man and one women plus their offspring in the fourth century, there were many bigamists in the church. Once the church squelched bigamy, they became very intolerant of it. This intolerance was one reason that kept them from effectively evangelizing people in other cultures. (To be fair, there have been some succes, both by protestants and Catholics.) Japan was lost to Christianity because the Catholic church would not accept a leading war lord who was a bigamist. This war lord was not going to divorce all but one of his wives, for he believed that he had a moral obligation to take care of them. So he helped to remove Christianity from Japan. Imagine how history might have turned out if Japan had been a Christian nation.
Luther clearly was against all religions that did not believe in the saving grace of Jesus Christ and did not believe that faith alone would get a person to heaven. This includes the Jewish religion as well as many others. Luther never lifted a finger against a Jew, although his words against false religions were very biting.
What do Catholics today believe regarding salvation? Is it by faith alone, or some other way?