For filtering out Ashburn's visitors, create a new segment with that browser and city as negative parameters. So it would be an "all visitors except these" segment. Then activate it in your reports.
But I think you should do more research before doing that.
Do you think all the hits from Ashburn are spammy? Try to add second dimensions to Location report. Look at source/medium, referral, hours, and organic search keyword (lot of times spammer bots access to your site with spammy keywords). Look at your server logs. There's a chance you can isolate that spammer bot and then filter it out in a cleaner way.
Look also at these two threads: http://webmasters.stackexchange.com/questions/76384/how-to-block-google-analytics-spam-from-hulfingtonpost-com/76390How to block google analytics spam from hulfingtonpost.com? http://webmasters.stackexchange.com/questions/75909/how-to-fight-off-referrer-spammers/75914#75914How to fight off Google Analytics referrer spammers?