Of course, I'm talking about people who are involuntarily celibate, not adherents to incel ideology, which is definitely right-wing.

While anybody can hold any ideology, one's political opinions are most influenced by one's material conditions, and this includes their body/appearance, etc. As a thought experiment, what politics would a hypothetical short, ugly person of color hold? The right, with their focus on the importance of genetics and the white race, would not hold this person in high regard. The left would be infinitely more accepting of this person. However, these traits that make this man repulsive to the right also make him unpopular with women. Because of course, short and ugly men are not known to be attractive to women, and it is known that women of all races find white men to be the most appealing. These things make him more likely to be an incel. Furthermore, this effect is compounded by the fact that the right is far more appealing to men that embody the opposite of these traits, as the left is not known for liking cis het white men.

Therefore, incels are more likely to be left-wing.