He is not redirected to the homepage of your site, but to the start page for that location.
If your widgets are set to filter for location, then only listings for the location chosen by your visitor will show.
Basically, if a visitor chooses to see all listings for a location by choosing that location, that is where he/she will be taken.
You are suggesting that if a visitor is looking at all the listings of a subcategory for example, that if they choose a different location, then only that subcategory for the new location should be shown. I think it is more logic that if you choose “Aalsmeer”, then you want to see everything in Aalsmeer for starters, and then you can always drill down.