I've run into people bringing this up when discussing hobbies and activities that to my mind don't violate anything in scriptures, and they can't cite any other verses, (I once had someone used this to argue watching the original Star Wars was sinful). I know we shouldn't put a stumbling block for others(kind of dependent on being aware of someone's potential weakness), and pursuing things that don't profit(presumably meaning don't let it it become an idol, or let it consume too much of your time). Then there's the obvious point about not violating your own conscious.
My point is, isn't this largely a personal standard? How should one handle an accusatory situation?
When it comes to hobbies/activities, I think any skill we have or excel in is a gift from God, such as sports, music, public speaking/story telling, painting, sewing, etc. So, for skill-based hobbies I believe it is fine to devote a lot of time to this, even our entire lives if God calls for/allows this.
If a hobby is lounging and watching TV or something similar, that could be a problem as this activity is not glorifying God. However, we are allowed leisure time. If a person is interested in Comic-Con, video games, etc. I believe that is allowed under leisure time.
Now, on what leisure activity is considered sinful or not glorifying God, there is discrepancy in the conscience levels/personal standards among Christians. Some Christians want to be built up all the time, such as through prayer, Christian movies, Christian songs, and when they don't get this they feel a bit empty. They want to be in the presence of God 100 percent of the time (in that manner), such that any other activity is a waste of time. Other Christians I feel have less of this need/desire to be built up, for whatever reason, where lesser time with God is enough to keep them charged. However there is the risk on the extreme end of not spending time with God at all. So, I think it comes down to that, some want/need to be built up all the time while others don't. I haven't watched Star Wars for awhile so I don't remember if there is anything in particular that is sinful, but maybe it is along the same logic as reading Harry Potter. If God is telling you not to read to Harry Potter, that is for good reason maybe He thinks you will be easily sway and tempted by witchcraft. However, God may not be giving someone else the same message, especially to someone who already thinks witchcraft is foolish. For example, God told the rich man to give up everything he had but He did not request this of everyone. God's message especially on these gray area matters may be individualized.