Calculation of occurrence of strings
By using a case a statement you can turn your magic strings into numeric values. These can be summed and a group statement defines how to organize the summation.

Edit: I've added a sort as it is likely you are interested in the "winners".

SELECT
    SUM (
        CASE WHEN vote = 'Yes' THEN 1 
        WHEN vote = 'No' THEN -1 
        ELSE 0 END) BalancedVotes,
    Name
FROM 
    myTable
GROUP BY 
    name
ORDER BY 
    BalancedVotes DESC