So they break our understanding of physics, but we are able to shoot them down?
And they have been showing themselves, just out of sight, for decades? Without any other effects?
If they’re aliens capable of interstellar travel, then they really suck at utilizing their technology, which would be far far more advanced than ours. Or they’re doing this intentionally, which also would make no sense. Other explanations are far simpler and more plausible.
The reason people mock this is because people go to the most outrageous conclusions before anything more reasonable, without sufficient proof to rule out simpler explanations. You know, a process which every other field of science uses.