Re: 2 Martial Arts
My question is related to the O/P's question, on the use of the word justifiable...
Justification in the legal sense would require the other guy to be trying to do bad things to you, first, then it's self-defense. Going first is assault/battery and it is You who are the bad guy.
Morally, from a peaceful mindset point of view, I'd say it's not justifiable, no.
But, from a real-world, need to protect yourself, if you didn't start the engagement, the bad guy continues it after you attempt to defuse the situation and attacks, then you do what is to hand to protect yourself.
And, finally, tactically... I'm coming from a place where I'm stacking 20years of aikido on top of 20 years-ish of striking arts ... there are VERY more iopportune times to use a strike than when the initial contact moment of the engagement is controlled by your aikido and the other person is out of position and off-balance. But, you still have to concern yourself with legality at that point as Katherine pointed out above.