It depends on the young researcher's courage :) but seriously, I think the science's fundamentals lie on polemics and discussion with other researchers and age shouldn't be the limit here. Of course there is always a problem with the science's culture and ethics which can differ in particular countries.
Thank you Ganesh and Agata for your valuable answers. Yesterday I finished writing of an article, to be published in the journal of electrochemical society, replying to a famous electrochemist who published a paper about the electrochemistry of iron in carbonate solutions