Curiously, the UK government made an argument to the contrary just recently when talking about when an alleged sex offender should have their name disclosed, which has been a big issue here of late after a wave of allegations about inappropriate behaviour by high profile media personalities going back many years. The argument was essentially that if you disclose the identity of a suspect before they have their day in court, you might encourage other victims to come forward with evidence that will build the case, which is presumably favourable if the suspect actually is guilty but obviously has severe potential consequences if in fact they are innocent but publicly associated with sex crimes anyway.
I'm not sure what the parallel with whistleblowing should be in a case of allegation but not yet a conclusive decision in court, but I'm pretty sure governments shouldn't be entitled to more protection against potential damage to their reputation than an alleged but not convicted sex offender.
(Just to be clear, I'm not commenting on the appropriateness of the policy toward disclosure of suspected sex offenders, just the double standard that would arise if the UK government objected to this kind of whistleblowing using your "innocent until proven guilty" argument.)