Egghead Professor Gerald S. Reamey commenting in the San Antonio Express-News:
But why shouldn't people be expected to "calculate" before killing someone? Why doesn't it matter whether someone has a knife instead of a gun or whether the person is armed at all?
Weak argument, Jerry.  You have failed to convince me that I must psychoanalyze someone who is forcing his way into my home.

Besides, your argument is based on a false assumption, and if you were really familiar with Texas law, you would know about that old "night-time" clause regarding forcible entry.

Back up to the very beginning of this commentary:
Years ago, I was a legal adviser for a Texas police department. Before going on vacation, I put my house on "special patrol."

In the middle of the night just before I left town, my wife heard noises outside our bedroom. Someone was shining a flashlight on the door leading to the patio.

Because I was also a sworn officer, I had a pistol close at hand. As we watched the door, we saw the doorknob start to turn slowly. While I trained my pistol on the door, my wife called 911. She was informed an officer already was at the scene.

As you've probably guessed, the burglar I was prepared to shoot was a police officer mistaken about when to begin the patrol on my home.
So he was there for a legitimate reason. Was there a legitimate reason for him to be opening your door at night without knocking first?  Sounds like he was about as sharp as a dull fence post.

On the other hand, here is another commentary in the Austin American-Statesman by State Senator Jeff Wentworth and Representative Patrick Rose:
We take strong exception to the American-Statesman's Friday editorial "Gun Bill Encourages Violent Confrontations" and its inaccurate portrayal of the intent and the scope of Senate Bill 378, which passed the Texas House and Senate and was signed into law Tuesday by Gov. Rick Perry.

SB 378 amends three aspects of Texas criminal and civil law with narrowly crafted language to benefit the innocent and not hinder the prosecution of lawbreakers in self-defense cases.

First, the bill creates a "presumption of reasonableness" for the use of force in response to an unlawful and forcible entry into an occupied home, vehicle or place of business or employment. A Senate panel added language to clarify that the presumption would not apply to people who provoke their attackers or engage in criminal activity.

Gang members, barroom brawlers and spousal abusers will not benefit from this change if they harm someone and try to claim self-defense. But victims of home invasions, carjackings and hold-ups will know the law is on their side when responding with force to a criminal attack.

Prosecutors can still bring charges, take cases before grand juries and rebut such presumptions if evidence exists that self-defense claims are not legitimate. But if no such evidence exists, the case probably should never have gone forward in the first place. The bill levels the playing field for crime victims and may even serve to prevent politics from entering into prosecutorial decision-making.

Second, the bill states that you have "no duty to retreat" from an attack if you are in a place you have a right to be, did not provoke your attacker and are not engaged in criminal activity. This was essentially Texas law until the mid-1970s. Under current law, the use of deadly force for self-defense outside the home is justified only "if a reasonable person in your situation would not have retreated." Victims should not be required to retreat simply because a criminal decided to attack them in a parking lot as opposed to waiting until they got home to commit the same crime.

Third, the bill protects victims from civil actions for using force authorized by law. The thought that victims could lose their life savings defending themselves against civil lawsuits brought by their injured criminal attackers is ludicrous. If we can offer more protection from this type of litigious devastation, we should do so.

Opponents falsely claimed in committee hearings on the bill that in the first year after Florida's landmark "Castle" law took effect, 13 people shot someone, claimed self-defense under the new law and got off free and clear. However, a review of those deadly force cases by an Orlando newspaper showed that authorities cleared five individuals, charged three and continued to investigate the remaining cases. Hardly the "get out of jail free" card opponents claim it is.
The editor had to add: "The Texas District and County Attorneys Association opposed the bill."  Of course they did.  Any law that would eliminate the possibility of another trial is a threat to their income.  Screw 'em.