Well, scientists are entitled to their political opinions, must like anyone else. However, what you describe, moral history of religions, wars, etc., falls outside science as you pointed out. unless such opinions are based upon the impact of scientific and technological issues of the time. However, scientists are right to point out when something advocated as science by the lay public isn't science.
"However, scientists are right to point out when something advocated as science by the lay public isn't science."
On a purely technical level, as related to science you are correct.... that is if one is Spock the fictional Vulcan and can separate the logic from the moral and emotional analyses that Humans make when forming their opinions.
Many self imagined objective science types can express quite a bit of out-rage when attacking a "notion" as "not of science", denoting moral and emotional out-rage...which of course raises the question as to whether they have truly reasoned said "notion" from a truly scientific basis.
We humans can't escape personal bias; we can at best account for it and factor such biases in as we strive to be as truthful, objective and as transparent as possible given the natures of our various circumstances and belief systems!