It is easy to demonstrate that radio interference can cause exactly the effect experienced.
Whereas no-one has ever demonstrated that ghosts even exist, let alone that they can cause EVP.
So how is the first explanation 'almost as weak' as the second?
We can't say for certain which is the correct explanation and which isn't, but one explanation seems far more likely than the other in that it is known to be possible and have repeatedly happened.
Is the evidence that EVP is caused by ghosts any different from the evidence that it is caused by Leprechauns, aliens or pixies?
Accepting all imaginable possibilities as being equally likely is not being open minded.