How are step parents able to be "fair" in conflicts between siblings?

Here's the story. A few minutes ago my BS6 was playing with a bat that the neighbor kids let him borrow/have. I am still unclear about that detail. My son made a comment that he was going to put the bat away. My SS13 decided to take it away and throw it over the neighbors fence. Of course, then my BS6 started crying. That's when I went outside to see what was going on. So the story I'm gathering is coming from the two boys. They both agreed to what happened, but my SS13 did not know for sure if the neighbor kids actually gave BS6 the bat. They trade toys all the time, so I didn't see an issue. Overall, I pretty much told SS13 that I felt he was trying to provoke BS6. (We've had issues like this before.) So was it fair to send SS13 to his room? It seems that ss13 tries to purposely try to get my son in trouble. Especially since we are going camping this weekend. They were told if they misbehaved, they wouldn't be able to go...

I'm not trying to be petty, nor am I complaining. I want honest opinions of how any of you would handle situations like this....since they tend to happen often with both of them.