You can never prove a negative. If people want to have suspicions, they will - even athletes without any documented glitches get mentions in these very pages for suspicious performances, or using the wrong doctor, or just riding for the wrong team. All of which are purely circumstantial.
Journalists can mention all these things (or missed tests) every time they report on Athlete X, if they choose. Free speech innit.
Is this the fault of the public, or the riders that cheated? Or both. It certainly isn't the fault of the clean riders.
Assuming anyone is clean ...