It has been my opinion that everyone acts in their own self-interest – or at least they do as far as they perceive it. The more relevant differentiation then is whether or not that perception or the individual's interpretation of that perception is thus rational.
As an example, I point out that someone who holds esteem for a faith-based belief that is predominantly (alleged to be) altruistic, will act according to how they perceive the belief, or perceive the extensions from it's dogma, to expect them to behave. In this case, even if the actions appear to be selfless in nature (altruistic), the reasoning for undertaking said actions extends from the individual's desire to conform with the belief or dogma.
I extend this further to belief in general, especially mystical belief in 'god' entities to suggest a filter to rational evaluation and esteem – what I refer to as god esteem (as opposed to self esteem). It is a conceptual collection of ideas that places itself between the individual and their own rational self-interest in that every evaluation of some thing or act as having to be subject to the suffix 'according to god'. (feel free to insert your own object of worship or arbitrary esteem for 'god')
In other words, the evaluation of self-interest then becomes subject to something being good 'according to god' or something to be right 'in the eyes of god' and so on. Consequently, it is one of the reasons I see 'faith based' ideas of any kind as fundamentally evil – because they either seek to or ultimately exist as an impediment that exists in man's mind between his rational faculties and his own rational self-interest.