"A firearm is property... you cant use deadly force to prevent the theft of property. So... If any of you had someone try and take away your gun and shot them... would anyone say... he tried to steal my gun and I shot him?"
VERY VERY VERY POOR analysis.
This isn't a VCR in your living room we're talking about.
If someone attempts to remove your firearm from your possession, they are not stealing your property, they are committing an assault upon your person.
If someone is willing to assault you while attempting to remove a deadly weapon from your possession, it's not a great leap to conclude that they would also be more than willing to use that deadly weapon to continue their assault on you.
Virtually every state that allows the carrying of firearms has some variation of the "I was in fear of great bodily harm/in fear of my life" as an affirmative defense for the use of deadly force.
In some circumstances, that affirmative defense even applies to using deadly force against an unarmed individual.
Just for interest's sake, I called an acquaintance of mine in Pennsylvania who spent over 20 years as the district attorney for a semi-rural, semi-suburban county, and gave him a synopsis of your arguments.
His opinion was clear -- that in the scenario described, use of deadly force is justified. Once an individual assaults you and attempts to take possession of your gun, the legal premise is that the individual will use your weapon against you and the use of deadly force is legally justified and legally defensible.
He said that while a DA could always bring, or attempt to bring, charges in just about any scenario, Pennsylvania law could make winning such a case very difficult.
Applicable Pennsylvania law - Pay special attention to the bolded sections
Pennsylvania Title 18, Chapter 505 - Justification
"§ 503. Justification generally.
(a) General rule.--Conduct which the actor believes to be
necessary to avoid a harm or evil to himself or to another is
justifiable if:
(1) the harm or evil sought to be avoided by such
conduct is greater than that sought to be prevented by the
law defining the offense charged;
(2) neither this title nor other law defining the
offense provides exceptions or defenses dealing with the
specific situation involved; and
(3) a legislative purpose to exclude the justification
claimed does not otherwise plainly appear.
(b) Choice of evils.--When the actor was reckless or
negligent in bringing about the situation requiring a choice of
harms or evils or in appraising the necessity for his conduct,
the justification afforded by this section is unavailable in a
prosecution for any offense for which recklessness or
negligence, as the case may be, suffices to establish
culpability."
and Chapter 505 - Use of Force in Self-Protection
"505. Use of force in self-protection.
(a) Use of force justifiable for protection of the person.--
The use of force upon or toward another person is justifiable
when the actor believes that such force is immediately necessary
for the purpose of protecting himself against the use of
unlawful force by such other person on the present occasion.
(b) Limitations on justifying necessity for use of force.--
(1) The use of force is not justifiable under this
section:
(i) to resist an arrest which the actor knows is
being made by a peace officer, although the arrest is
unlawful; or
(ii) to resist force used by the occupier or
possessor of property or by another person on his behalf,
where the actor knows that the person using the force is
doing so under a claim of right to protect the property,
except that this limitation shall not apply if:
(A) the actor is a public officer acting in the
performance of his duties or a person lawfully
assisting him therein or a person making or assisting
in a lawful arrest;
(B) the actor has been unlawfully dispossessed
of the property and is making a reentry or recaption
justified by section 507 of this title (relating to
use of force for the protection of property); or
(C) the actor believes that such force is
necessary to protect himself against death or serious
bodily injury.
(2) The use of deadly force is not justifiable under
this section UNLESS (my emphasis) the actor believes that such force is
necessary to protect himself against death, serious bodily
injury, kidnapping or sexual intercourse compelled by force
or threat; nor is it justifiable if:
(i) the actor, with the intent of causing death or
serious bodily injury, provoked the use of force against
himself in the same encounter; or
(ii) the actor knows that he can avoid the necessity
of using such force with complete safety by retreating or
by surrendering possession of a thing to a person
asserting a claim of right thereto or by complying with a
demand that he abstain from any action which he has no
duty to take, except that:
(A) the actor is not obliged to retreat from his
dwelling or place of work, unless he was the initial
aggressor or is assailed in his place of work by
another person whose place of work the actor knows it
to be; and
(B) a public officer justified in using force in
the performance of his duties or a person justified
in using force in his assistance or a person
justified in using force in making an arrest or
preventing an escape is not obliged to desist from
efforts to perform such duty, effect such arrest or
prevent such escape because of resistance or
threatened resistance by or on behalf of the person
against whom such action is directed.
(3) Except as required by paragraphs (1) and (2) of this
subsection, a person employing protective force may estimate
the necessity thereof under the circumstances as he believes
them to be when the force is used, without retreating,
surrendering possession, doing any other act which he has no
legal duty to do or abstaining from any lawful action. "
)