A card like that shows a jury that a defendant in a wrongful death case had at least a thought of the possibility of taking someones life.
If as a legal gun owner wether you carry or just have it in your house and you haven't "thought about the possibility of taking someones life" then i would be more concerned about that than about a card with a statement of your rights on it.
When i joined the Marines at 18 that was the hardest question i had to ask myself before i signed the papers and raised my hand, could i pull the trigger if i had to. There are reasons they teach you codes of conduct and how to react in situations, there is also a reason they give you a printed manual to carry and have lawyers in the field with soldiers now. To make sure you know your "rights" and the rules of engagement.
Having said the above there is also a reason you go to classes before you get the "right to carry" or to become a police officer. To teach you when it's appropriate to use deadly force. How many times a day do we see news stories about a police shooting where the officer "thought" his life was being threatened?
I think the point here is being missed and i stated it before. Wether you hand the officer that card or not, first shut up, volunteer no information unless asked and then only give the facts, make no judgements or go into any type of guessing what might or might not have been a motive, request a lawyer as soon as possible. The only way to protect yourself now days after any incident is to shut up, know your rights, and get a shark....errr lawyer.