What constitutes 'proof' can often be subjective, and is often influenced by our own bias. Often you see instances whereby someone forms an opinion and then accepts as proof anything that supports said opinion whilst dismissing anything that fails to do so. For one man there may be compelling evidence (proof) that something is so. Another man however may dispute this proof and even present 'evidence' that he firmly believes contradicts the others said proof.
We see the above all the time in the ever changing world of medical science. For example there are many extremely well respected medical professionals who state without reservation that the consumption of red meat greatly increases the chances of one suffering from one or more serious health conditions. People who are vegetarians, vegans etc are more likely to accept such views, and the research/studies that such medical professionals cite, as proof that eating red meat is bad for your health. But there are other equally qualified and respected medical professionals who dispute the proof offered re the damage on ones health that red meat can cause and who cite various medical studies/research etc as proof of their views. People who eat red meat are more likely to be persuaded by their evidence than that offered by those who hold different views.
As stated, 'evidence' is often subjective and the weight we give it is usually influenced by the biases that we all have. So whilst it is often positive to debate different points of view we should be generally wary of insisting that our view is the only correct one, and in trying to insist that others see things as we do. Having said that, if you are involved in a debate about something eg the existence of ghosts, then I think it not unreasonable to expect that both sides put forward their 'evidence' as opposed to just one.