Let us stipulate the basic sensibility of your question, and consider its necessary consequences, disregarding the essential imprecision of a term like "angels"

Let us stipulate the basic sensibility of your question, and consider its necessary consequences, disregarding the essential imprecision of a term like "angels" for the sake of interesting discourse. We have, then, "...governments and religious institutions actively engaged in telling us we are not [angels]". We may presume, from the fact that this behavior persists throughout human history, that these agencies see some concrete benefit in so doing; while of course one may find individuals and institutions acting against their own interests, such behavior cannot lend itself to survival across centuries. Were all humans angels, would those who constitute these doleful organizations see such benefit? I find it doubtful; while "angel" is not properly formulated here or anywhere else, we can assume from context that the cardinal quality of such a creature would be a perfect altruism, one to which gain of self at expense of another would be not merely distasteful but insuperably repellent, if indeed conceivable at all. The necessary conclusion, then, is that, while there may be some humans who are actually angels, all humans cannot possibly be angels, because no true angel would act in behalf of a scheme centered upon convincing other angels they were in fact not angels, to the real and significant benefit of the schemers. We therefore find ourselves with the following dilemma: either not all humans are angels, and to have stable and effective government, we must find some way to rule which accounts for this fact; or, not all things which have the human semblance are human, and to have stable and effective government, we must identify and exterminate the unhuman creatures which beset us, down to the last not-man, not-woman, and not-child, in order that we true humans may govern ourselves, free of their blight, in whatever fashion our shared perfect altruism sees fit. Perhaps you feel I have unfairly caricatured one of these points of view. If so, I commend to you a careful study of the history of the twentieth century, in which the latter opinion may fairly be said to have run rampant across large swaths of the globe.