Because if it isn't passed into law when an election is called Johnson can dissolve parliament at that point and the law won't get passed prior to Oct 31 so we could leave with no deal at that point.
When Labour say that they want no deal off the table they really mean no deal off the table for Oct 31, they are prepared to campaign against no deal as part of an election once Oct 31 has passed and we are still in the EU.
A bit Rich for you to accuse others of racism tbh. I'm sure I recall you doing racisms on here.
What happened to wisdom, anyway? The people who voted us in in '75 have had longer to see how it works, and besides, no-one knows what the long term consequences of either leaving or remaining would be.