This is obviously some strange use of the term "non-aggression" that I wasn't previously aware of.

So suppose someone is badly injured and dumped in your garden, and you have no way to get them off your property without killing them (because of their injuries), do you seriously find killing them an acceptable course of action?

I am pro-choice myself, but if I considered abortion "categorically the killing of a human being" and saw no better argument for permitting it than an analogy with non-deliberate tresspass then I would switch sides in a foetal heartbeat.

(If you want an argument along roughly these lines, may I commend to you Judith Jarvis Thomson's "violinist" thought experiment? It seems to me strictly better than this, for anyone who doesn't think property rights are the only thing that matters.)

[EDITED to fix the spelling of Thomson's surname.]