to advise or not advise ...that is the question

...I'm torn between offering advice to a colleague and minding my own business ~  the advice is not of a 'personal nature' - Lord knows I'm not good at that kind of advice ... but is based on many years of doing the same job ... admittedly I have offered suggestions in the past, received well but not acted upon ... but it's not the deaf ear I fear, rather the opinion that it's not my business ...the person for whom the advice is intended has used (in my opinion) poor judgement by using social media to 'vent' his frustration with regard to a professional relationship ~ a faux pas that I feel will undermine his professional success and integrity ~ this no-no has occurred at least twice to my knowledge and I feel an obligation to bring the possible consequences to my colleague's attention ... and to explain that a rant in a social media forum is not professional and reflects more poorly on the 'ranter' than the 'rantee' ...several comments followed the initial offering and not all of them reflected the opinion of my colleague ... since the original rant cast disparaging remarks on a 'business partner', should the wrong person see it, it could have effects that I don't believe my colleague has guessed at ...what do I do? I feel compelled to say something, at the same time I feel that I should not be 'censoring' another's words ...