I don't like him, nor his ideology, but he is an elected representative of his constituents and elected leader of his party.
Maybe, but he's hardly representative of the nation and this is a strategic national issue.
Working on rounded numbers for ease, Corbyn received 250,000 votes in the Labour leadership election. In the general election Labour, as the losing party, received close to 9,500,000 votes out of a rough total of 25,000,000 votes. That means Corbyn became Leader of the Opposition something like the equivalent of 0.01% of the national vote and something like the equivalent of 2.5% of the Labour vote at the last general election.
I wouldn't therefore describe him or his views as being particularly representative and he would do well to listen to the experts employed to provide specific politically based advice as STB so correctly notes. Furthermore, as a key component of the deterrent capability is the willingness to press the button, to publically announce that you wouldn't ever press the button effectively renders the capability redundant and as a result the nation potentially weakened. Corbyn clearly has much to learn about stepping up from local reactionary to potential statesman.