Yes, it is possible to be a peaceful muslim. A higher percentage of peaceful muslims exists in areas with a culture that does not value religious warfare, and where the religious leaders do not preach violence.
(The United states currently has had one violent event related to religious violence, which if I remember right was carried out more by immigrants than by homegrown muslims and converts. East Asian countries with muslims have had problems here and there, but many of them have come about in areas where large groupsof both muslims and non-muslims exist in the country (Philippines, Thailand), and may be hard to separate from any sort of conflict between multiple religious groups. Malaysia and Bangladesh are not known for religious violence, though that may just be from missing information on my part. Similar problems also exist in parts of Africa, but the religious element may be hard to separate from other multi-group fighting.)
The full argument was something along the lines of: In areas with Polygyny, some males will have trouble finding females for themselves (Which is a pretty bad sounding way to say it, but to continue). However, by being offered females from suicide bombings, they now have an opportunity for females if they carry out a bombing.3. Suicide as a sex-substitute? Where are the exploding Catholic priests? Vans with gas cylinders driven by Carmelite nuns? Buddhist monks with box-cutters boarding airplanes?
Since Catholic priests and nuns, buddhist monks, and any other equivalents in other religious choose to give up females (Or males, for nuns), rather than being outcompeted for them, they will have less of a reason to want to do something just to get some. In addition, since those religious don't offer virgins as an afterlife reward for violent martyrs, there is no reward for carrying out bombings.
I would still argue the polygamy arguments, for the reason you mentioned earlier about it becoming less common. It does make sense that polygamy in early times, pus the virgin rewards, would have built up a warrior/death tradition that currently motivates modern day people, but that would just have the same effect as any other type of warrior/martyr tradition.