In my opinion, appointing someone as CEO can not be base purely on professional performance. The CEO position is too public to ignore personal actions. Eich is of course allowed to have his own opinion on issues, such as gay marriage. But now being CEO of Mozilla, Mozilla has to ask themselves if his personal views are in line with the views/mission of Mozilla as a company.
The freedom to have your own opinion on things does not protect you from the consequences of those opinions.