Yours wasn't either, they are just analogies.
You are still making the same apples-to-oranges comparison. In your example you see a dog of a breed that you know has been dangerous, and you took appropriate steps to protect your child from that danger, because you had a simple ability to do so.
But would you, seeing the dog in the street and knowing nothing about it, run it over with your car since you know that SOME pit bulls are dangerous, therefore ALL pitbulls deserve to be punished?
Taking things out of analogy and back into the imperfect world we live in -- many people justify their racism by the argument that blacks are more likely to commit crimes, therefore it just makes sense that they should be allowed to associate only with whites. Or just with people just like them, because that is what makes them most comfortable.
I can't argue with that -- everybody feels more comfortable dealing with people that are like them, and thinks that is simply the safest and most acceptable association.
But Society suffers if everybody acts in their own selfish interest in that way. So we as a society, FOR THE COMMON GOOD, have used government as a "persuasion" to force people to associated in certain public ways with those they feel uncomfortable with. This association has in fact led to some people being harmed who would in fact have remained unharmed had they been allowed to to things "their way".
Stores are shoplifted by a black man, who they never would have let into their store if not for the anti-discrimination laws. And that seems wrong, but it isn't. Sure, a single person denying blacks access to their store wouldn't really matter, but if many people do it, blacks as a group are penalized even though most are fine upstanding citizens.
Having been denied access, denied equal treatment, they can become a problem that otherwise would not exist. (They also have their constitutional rights denied, but I ignore that aspect for this discussion since constitutional rights are not in play in the ports case).
Your child is put at risk for the common good. We make children get vaccines. This is a risk. However, if nobody got vaccines, many more children would die than end up dying from the vaccine.
But, in the perfect world for your child, every other child would get a vaccine, and your child would not. Since all others were vaccinated, your child had no danger of getting ill. And since your child skipped the vaccine, there is no danger of dying from the vaccine.
So why doesn't this happen? Because if you ALLOW one to skip vaccines, many will realise this benefit, and they will skip vaccines, and then there WILL be a risk of sickness and the benefit will turn into a liability.
Your blanket contention that you increase the risk of terrorism by giving access to muslims is correct. At this time muslims are disproportionately represented in the world of terrorism, and avoiding all contact with muslims would lower your risk of being effected by terrorism.
But society would be harmed for your gain, and that harm is greater than the gain. We need to lower the risk of muslims being terrorists, not increase muslim isolation and hatred for us. Rejecting the port deal simply because it is an ARAB company and we know some arabs are terrorists harms our national interest, and perversely harms our national security.
If there was a real security issue solved by that denial, you could weigh the benefits and risks to society, and make an informed choice. But since there is no real security issue, only the vague perception of "dread" about the idea of a muslim company controlling the ports, there is no rational basis for judging security to be improved by denying the deal.
If you really want to get ports back into U.S. hands, denying the deal is completely superflous to that goal. You are going to have to get the ports out of the hands of P&O anyway -- it will be no harder to get them back from DP World. If this was a transfer from an american company, the argument would have merit, but since it is not, stopping the deal doesn't put you a single step closer to the goal of american control of ports.