Unfortunately, Twitter doesn't offer the option to mute or filter out hashtag conversations. Fortunately, Tweetdeck does. Under settings, click on "Global Filter" and then enter the hashtags you don't want to see in your stream in the "Containing Words" field:
If you decide you do want to follow the hashtags again, just clear these settings.
PS: Hate it when people sync their Facebook or Pinterest accounts to their Twitter feed? You can filter these out on Tweetdeck as well by simply including them in the "From Sources" field.