From perusing some of these vile forums, some observations...
-they HATE the fact women no longer NEED men. This makes men useless.
-They HATE the fact that the typical work men do is undervalued in society - e.g. manual labour is overwhelmingly done by men and these jobs are largely underpaid with a low social status. They believe that men do all the important, necessary jobs in Society but this isn't realised by women, not western women anyway - most criticism is of western women on these incel forums.
- They HATE the fact that there is more competition in the workplace now that women have entered the workplace.
They hate the fact women are getting 'above their station' and overtaking men, e.g. in education, very bizarre as according to them all women are stupid
-They HATE the fact women can have and raise babies without a man.
-They HATE the fact that women apparently ONLY go for Chads (very good looking men) and never consider any other man, despite this being not at all true.
- They HATE the fact that these days woman can have sex without consequences (birth control etc). Which also makes little sense as surely these means there's more women to have sex with but hey ho.
-They HATE the fact they are being called out on their misogynistic behaviour and that it isn't acceptable (in public) anymore. Which drives them to these vile forums.
-They HATE older women (aka women who won't put up with their crap!) They feel that women are ruined past the age of 25 both physically and emotionally. Which leaves them with a very small pool of women to fight over as even men in their 40s and 50s plus on these forums apparently won't touch women past these ages. 
-They HATE that women can get sex at any time whenever and where ever, even if she is old, fat and ugly....despite them also declaring that they won't touch any overweight woman over 25...
In other words, it's insecurity. The men who are underachieving in society feel this strongest and like a snake or a rat, a scared snake is also a dangerous snake...
Of course it's nothing that they need to improve on. Maybe they should have worked harder at school etc etc etc. Oh no it's all our fault. 
But yes I think it's not just the incels, all men feel this to some degree. This afternoon I was at the fuel station filling up my tyres and some guy on a motorbike nips in first - I didn't care I wasn't in a rush. He asked me to read out what the PSI was when he started filling his tyre, I told him (it was incredibly low) his mate then ran over and took over ignoring me completely as if I was unable to do this despite regularly using the machine to fill my own car tyres and being able to read. Pathetic really, these were perfectly nice men but obviously being a woman I am unable to do certain things in their eyes.
A member of my own family recently commented on a woman 'asking for it' due to what she was wearing - apparently it's not the man's fault if he's tempted- he can't help his biology
... this coming from a man who also calls himself a feminist. 
It really is like they do see us as a lesser species.
And I genuinely think most men think this way to some extent, even the nice ones, whether or not they admit it.