The second amendment is designed to affirm the ordinary citizens right to defend themselves. As with the bill of rights, the rights simply exist, they are not "given" to us, therefore they cannot be taken away, unless we let it.
For military and police to have the only weapons would be suicidal for us as a country. We would be at their mercy.
If a rapist comes into your house with a weapon and you have nothing to level the playing field, you will get raped and possibly die. If you are armed with a firearm, he who shoots first accurately will live to tell the tale.
I will take my chances as an armed citizen. No one talks about limiting free speech, limiting unreasonable search and seizure, limiting right against incriminating yourself, etc. Personally, I think more people should be armed. When crazy whackjobs show up in a gun free zone hell bent on death and destruction, they are usually successful because law abiding citizens won't carry in gun free zones because it is illegal. A person hell bent on murder has never once worried about carrying a firearm in a gun free zone or shooting someone with a weapons they aren't suppose to have.
Banning the AR-15, which was NOT used in Orlando, isn't the issue. Those types are rifles are used in about 2% of intentional homicides. Handguns are used in about 80% of intentional homicides. Firearms are also used in about 100% of self defense incidents.
Chicago has a practical ban on handguns. They kill as many people every month as your typical mass shooting. Ergo, gun bans don't work.