But you CAN say it's false if the evidence shows it is something else entirely. We've done that with UFOs, debunking them one at a time. If you say "Interstellar craft are here in our atmosphere" it's up to you to prove it, else it remains unproven. You can't really prove a negative, so it's unrealistic for you to demand that. If you say "THIS picture shows an interstellar craft", it can be disproved by showing it's, say, a butterfly.
The current count is many thousands of butterflies, beetles, birds, balloons, drones, kites, reflections, etc to zero interstellar craft. (And the LIZ is still the LIZ.) As for "wormholes", you'd have to explain what one even looks or acts like. Good luck.