Generally speaking, people almost always find some way to justify their actions to themselves, if they even think about what they do in ethical terms at all.

They justify it by convincing themselves their actions are necessary to feed their families, or they think what they do isn't as bad as what someone else does, or everyone else is doing it, or they'll compromise for now but do better later, or they just don't care about most others and are looking out for themselves, their friends and family.