I would say it's unusual to defend as vigorously as you do someone whose political views you do not actually share. I guess you just enjoy playing devil's advocate which is fair enough but it somewhat weakens your debating position IMO.
I don't see why lack of commitment to a cause = a weak debating position. I have seen various points raised against Corbyn which add nothing to a sensible debate. His age, dress sense and facial hair are irrelevant.
As far as I can see the arguments against Corbyn are weak leadership and an inability to appeal to the wider electorate.
His leadership has been seriously undermined by the rebel PLP. Would a sympathetic PLP find his leadership adequate? No-one knows, but Emily Thornberry for one strikes me as no fool and she works with him OK.
His wider appeal has not yet been tested. Politicians have increasingly relied on media support in recent years. People are now looking for other sources, however. That's why Corbyn has support; people increasingly don't trust the media to be impartial.