IRationalizations abound here, little guy vs. corporation, etc. But those arguments I think are not so important as the key matter of coming face to face with the fact that how Axanar has behaved must be interpreted as having crossed way too many boundaries.
Here's my take on it - from a totally common-sense, non-legal perspective.
When I was little, I remember playing with my friends. Sometimes we would play in my yard, sometimes in my friend's yard. Occasionally, and without thinking too much of it, we would wander and find ourselves playing in some other neighbor's yard. A bit surprising to me looking on it with age, but most of my neighbors were pretty cool about it - other than maybe a "don't step in the begonias", they just let us keep playing - because we weren't harming anything or causing any problems.
But if they did tell us to stop playing in their yard, we would say "okay, yes ma'am (or sir)" - and we would comply. We wouldn't argue with them, and we certainly wouldn't be so graceless as to stand our ground and say "make us leave" - or, worse, "hey, I have a right to play in your yard."
"Star Trek" is C/P's yard. Fan films that play in it that do so under C/P's good graces - and they should not be bratty or combative when asked - or told - that they can't play in C/P's yard any more. It's that simple. To do otherwise demonstrates why people - and corporations - eventually put up fences and "do not enter" signs on their "yards".
(And, putting my legal hat back on - and extending the "yard" metaphor to the law - there is a very real, very old doctrine in real property law called "adverse possession", which states that, if you let someone be on your land and don't take action to evict them when their presence is "open and notorious" and they claim they have the "right" to stay there, you eventually give up ownership of that part of your land to that person. So, IMHO, everything we see in Axanar - from the production crew to the "fans" - claiming they have a right to use C/Ps "yard" because they "don't like what C/P is doing with it" is ultimately only forcing C/P to take stronger measures to "evict" them, because not doing so could result in C/P losing some of its rights in its property.)
M