Sigh. I feel like my entire point is getting missed, so I'll try again:
Yes, I'm sure there are other sources to back up your beliefs just as I could probably find sources to back up mine. I'm not saying Pisces is onlya liar and always will be. That's just plain silly!
You said I was conflating the meanings behind Neptune, Mars in the 12th house, and Mars in Pisces but Robert Hand's interpretation of Mars in Pisces is parallel to what I've read about Mars in the 12th house, so where is the problem in that regard? Their expression (Mars in the 12th and Mars in Pisces) seems pretty interchangeable.
I understand what you're saying about Mars in Pisces shrinking away from someone who is aggressive. I have Mars in the 12th, I react the same way to people who come on too strong. That very reason is why I'm sensitive to how I come off to people I'm interested in getting to know better. That, plus this person's reactions to me lead me to believe I am not "dominating" him in any fashion. A further side note would be that I mentioned his Mars aspecting Pluto and how that made a difference, but so far we've been stuck on this.
The crux of this discussion is figuring out what constitutes as "lying". You don't see omission as dishonest - I do, and therein lies an impasse.
Too many modern astrologers conflate planets, signs, and houses. They are not the same. A planet works like a noun in a sentence, the "what." A sign is like an adjective or adverb: it indicates "how" or in "what manner" a planet operates. A house works like a prepositional phrase. It shows "where" or in what "domain of life" a planet operates. An aspect shows how pairs of planets operate.
Each planet has rulerships. Mercury rules liars, not Mars. Mars rules one's assertiveness and aggression. I hope we're clear on that. So no, lying is not a quality of Mars, independent of its sign. The chart you posted shows Mercury square Mars and Mars conjunct Jupiter. Jupiter expands what it touches, so it can give a propensity to exaggerate.
Lovely Miss Aries, I don't know how you would rate your ability to synthesize a chart, but that is what you need to do to determine how a planet operates. You have to get beyond planets-in-signs and planets-in-houses. Maybe you
do this already, and if so, I'm sorry.
What does your Mars aspect?
Basically the 12th house deals with matters that are hidden to us, or obscured to us, even though they might be highly obvious to everyone else. Sometimes this hidden quality is a choice, because the 12th deals with people who are voluntarily sequestered, like monks in a monastary. It deals with people who are involuntarily shut-in, like prisoners and hospital patients. Traditionally the 12th dealt with "secret enemies" (i. e., enemies who are hidden from your view) unlike the 7th house enemies who are the ones you know about.
So with Mars in the 12th, you may not be clear about your natural assertiveness and aggression. You may obscure it from view, or try to. You may come across as aggressive to others even when you do not intend to. Donald Trump's Mars is in the 12th house conjunct his ascendant, for example!
Pluto is a powerful planet, so in the chart of interest, it can make the person more assertive than we would otherwise expect. Pluto has an underworld connotation, due to its being named for the Roman god of the underworld. While this could come across as deception, here's the thing.
You'd expect planets to operate in the domain of life (house) and in the manner (sign) of the horoscope, with modifications according to aspecting planets; or perhaps the essential dignities and debilities.
Maybe it would be easier if you indicated what you think Mr. Pisces Mars is lying about.
Whether or not "omission" is lying depends on the circumstances. If you're developing a romantic relationship with a man and he doesn't tell you he's married, that's deceptive. If it's an invasion of his privacy, he's under no obligation to divulge.