What if Earth's atmosphere was toxic to aliens the same way their atmospheres are toxic to humans

So, for example, if humans were to visit Mars or Venus, they would be asphyxiated by the gases there. Mars' atmosphere is too cold and thin for liquid water, and mostly carbon dioxide, while Venus is crushing and acidic. <br><br>And Jupiter's moons all have their own toxic atmospheres to humans. Io is mostly sulfur dioxide, Europa's atmosphere is mostly O2, and Ganymede is also mostly O2 but its atmosphere is too thin anyway. <br><br>Humans could possibly visit Titan, but only with O2 and warming equipment to keep from freezing. <br><br>But what if aliens, who evolved in atmospheres unlike ours or our solar system's planets and moons, ...found Earth to be an inhospitable planet as humans would find their home planet's atmosphere hostile? <br><br>Wouldn't it be funny if Earth's atmosphere is toxic to aliens, and they are as unable to live on Earth as humans are on Mars? Jupiter?