Should one condemn all of Newton’s writings, because he dabbled in alchemy?
Naturally not. And as an aside, Newton did not dabble in Alchemy. I remember being taught that he wrote as much on alchemy as on physics, but I can't find a source at the moment. This article has some related info:
http://www.wired.com/2014/05/newton-papers-q-and-a/
More intriguingly, Lynn Thorndike suggests that newton's astrological belief in 'action at a distance' was key to his discoveries in the field of gravity.
I'd also point out that while Luther got rather more irascible in his later life, he was also responsible for penning, "That Jesus Christ Was Born a Jew," which was radically philo-Semitic for its time.
Shalom