Socialist Rifle Association

This reads to me as "I am not debating my right to exist [as a trans person or trans supporter]. I'm ready to defend myself and my allies if need be, to whatever extent is necessary. Back off or else."

So it comes across as a call to be ready to fight back, which would mean that if you're comfortable owning a gun or another weapon (or more comfortable owning a gun than not within the context of the current sociopolitical climate), it would be wise to have one on hand. I don't take it as a literal call to arms, it's more like an alternate, more direct/specific take on the Gadsden Flag. Not overtly hostile, but a clear warning that aggression will be responded to with an appropriate measure of self defense.