It's not about who's "in the right class" it's about our interests as working class people versus the interests of the ruling/boss/employing/bourgeois/whetever class. The two are ultimately irreconcilable.
And it's not about individuals, per se. There's no point trying to go about saying "this person's in this class, that person's in that class" unless you're talking about clear examples, for instance, the CEO of IBM is a member of the boss class, but it's not as clear cut when you're dealing with, say, a person who is due to inherit a fortune once their parents snuff it but is currently working a crap minimum wage job and living in a bedsit in a shitty part of town. Bottom line, class as applied to individuals can get a bit messy and it's too complicated to bother with a lot of the time.