I dunno, it just reeks of the culture of suspicion in communist China. A product of that place and time.
My own idea is the 'used car salesman' idea of the universe. (Reeking of my own mind and place and time). To me, economics will rule in the galactic community. In that water, metals, energy, it's all cheap and everywhere. No need to have any competition over it. No, the only scarce thing is life and then even more it's intelligence. Any other civilization will be desperate to get rights over us and our history.
So, to me, the aliens will come to us loud and proud. Balloons and banners.
And of course, a contract as long as a the rings of Saturn, with print as small as the atoms.
We shouldn't be wary of the weapons, but the lawyers
Charles Stross' Singularity Sky seems the most reasonable to me. Superintelligent computers trade unimaginable technology (their infintely replicable trash) for their most sought after asset (new forms of entertainment) and then just piss off to another world having completely bent our cultural development.