Why is the communist symbol (☭) an emoji?

There are two problematic premises in this question.

The first is that the primary semiotic of the hammer and sickle is “mass random murder of dissidents”, rather than “common ownership of the means of production”. The legacy of Communism may have been tainted by what Lenin and Stalin did; but that does not make the hammer and sickle a hate symbol banned the world over. In some Eastern European countries, at most (Hammer and sickle – Wikipedia). And there are still plenty of Communist parties left in the world.

The second is that this is an emoji. As in, cutesy symbol intended for SMS use, promulgated by mobile phone manufacturers in Japan because they got lazy about rich text encoding, and sanctioned by the Unicode Consortium in a move that I will never ever forgive them for.

But the Hammer and Sickle symbol is not an emoji. It was not brought in by phone manufacturers, and it was not intended for Communist member parties to send cutesy messages to each other.

The Hammer and Sickle, U+262D, belongs to the Unicode Miscellaneous Symbols block. You can discern why it is there, by looking at its immediate neighbours:

☠☡☢☤☥☦☧☨☩☪☫☬☭☮☯ (U+2630 through U+263F)

Five medical/hazard symbols, followed by eight religious symbols, followed by the Hammer and Sickle, the Peace Sign, and the Yin Yang symbol. These are various symbols of creeds and ideologies that have been prominent in recent years. The Hammer and Sickle belongs there for the same reason the Peace Sign belongs there. And the Peace Sign is not there as an endorsement of nuclear disarmament.

Although I note with merriment (Peace symbols – Wikipedia) that the South African government tried to ban the Peace Sign in 1973, because it was used by opponents of apartheid.