Your question seems to presuppose quick, cheap, and reliable transportation between our planet(s) and theirs. (And that being wiped out by each other's microor

Your question seems to presuppose quick, cheap, and reliable transportation between our planet(s) and theirs. (And that being wiped out by each other's microorganisms is not a concern.) Vs. if we've technically "encountered" them, but it takes (say) 100 years and $1B per person to travel in between? Only the most fanatical - who probably can't afford the time, nor ticket price - might support any policy except peaceful coexistence.