The following tables display mean nihilism scores from the years 1998 and 2008, computed by taking participant responses to the 5-point scaled GSS item on perceived lack of purpose in life and inverting the averages for ease of reader comprehension. The higher the score, the more nihilistic the group is. One standard deviation is .76 points on the nihilism scale.
First, among men in their forties or older (who have thus had ample time to get married if they desired to do so) who are married (or widowed) and those who have either divorced or never married in the first place:
About one-fourth of one standard deviation's difference, equivalent to the nihilism gap between the middle class and the underclass.
Some of those guys are inevitably unmarried not because they willingly choose to be flying solo but because they don't really have a choice, though. Some guys are just too unattractive to women to ever land one. C'est la vie.
So, consider the same by the number of lifetime notches in the belt, again aged 40+:
|# of women||Nihilism|
Those with one lifetime partner or whose lives have been characterized serial but long-term monogamous relationships are a little less nihilistic than the club hoppers are, but the men who don't (or can't) get any at all clearly are the ones who feel tend to feel that life does not serve much of a purpose.
This doesn't disprove One's assertion, of course--I'd guess a significant chunk of the Manosphere is comprised of bitter men who've faced unending frustration in their relationships (or lack thereof) with the ladies.
GSS variables used: NIHILISM, NUMWOMEN(0)(1)(2-5)(6-10)(11-20)(21-500), SEX(1), AGE(40-89)