List all tags associated from specific content type only?
Thomas - the answer is going to assume you are using Drupal 7, since you didn't specify.

Likely, the issue here is that you are using Taxonomy terms as the base of your view and therefore not able to select Content: Type as a filter.

To get that filter to show up, you need to add a Relationship (under the Advanced section of the view options) for Taxonomy term: Content with term.

After you do that, then Content: Type will show up in your filter list.