If you work a menial job, or your family doesn't respect you, or you're looked down on by society - or maybe a combination - then your commute home is maybe the only time you have real power, protected by a big metal shell. So the anger at cyclists is more about 'how dare they slow me down when during the small pocket of time in my existence when I wield power?'.
I'm a long time cycle commuter relucantly turned auto-commuter. I thought I'd start hating cyclists too once I joined the herd but they're practically a non issue.