I think the actual beliefs of philosophers are more open to dualism than the "discredited" quote implies. The philosophical survey shows a majority of philosophers to be physicalists (56.5%), but with 27.1% non-physicalist, and 16.4% other -- there is certainly a lot of room for dualism and idealism among contemporary philosophy. http://consc.net/papers/survey.pdf As the question notes, theism generally presupposes dualism, and with 14.6% theists among philosophers (and another 12.6% other, which pretty much also requires dualism or idealism) the dualists among philosophers are plausibly between 15-25%.
Note the SEP entry on dualism itself is not nearly as dismissive as that sentence fragment -- here is a key quote:
although dualism has been out of fashion in psychology since the advent of behaviourism (Watson 1913) and in philosophy since Ryle (1949), the argument is by no means over. Some distinguished neurologists, such as Sherrington (1940) and Eccles (Popper and Eccles 1977) have continued to defend dualism as the only theory that can preserve the data of consciousness. Amongst mainstream philosophers, discontent with physicalism led to a modest revival of property dualism in the last decade of the twentieth century.
Note "out of fashion" is a far cry from "discredited". https://plato.stanford.edu/entries/dualism/
A good discussion about that fashion is in Papineau's The Rise of Physicalism: https://www.academia.edu/819823/The_Rise_of_Physicalism Papineau traces the decline of dualism to the success of biochemistry, and the simultaneous failures of vitalism in biology, plus the successful reduction of much of chemistry and physics to fundamental physics forces and particles. Physicalism would therefore be a "progressive" Lakatian Research Programme: http://people.loyno.edu/~folse/Lakatos.html
However, the failure of reductionism in general, and in particular the failure of reductionist philosophy of mind, has begun to reverse that fashion. https://plato.stanford.edu/entries/scientific-reduction/ Physicalism is becoming a "regressive" program, and dualism is under increasing reconsideration.
Since the end of the 20th century, the credibility of dualism has continued to grow.
Even Jaegwon Kim is now a dualist: https://www.amazon.com/Physicalism-Something-Princeton-Monographs-Philosophy-ebook/dp/B005646D3I
Here are four more references that show the increasing vigor of dualist thought: