You can do this as below (note: Check for the performance issues before implementing)

declare @date datetime

select @date=MAX(date) from #mytable where method='B'

;with CTE

as

(

select [DATE],method from #mytable where method in ('A','B') )

select [DATE],method from cte where (method='A' and [DATE]<>@date) or (date=@date and method='B')