The real life firewalls

Everywhere apart from the computer life, I can see a firewall in every second of the life. The firewall becomes inevitable to lead the life. But what makes me concerned that where does it exist and why does it exist.
The situation becomes difficult when two or more firewalls are to be constructed on the same place.
Approximately one year ago during a chat in yahoo the other person was probable some girl from Philippines. During the chat about painting and hobbies once I called her dear, a sudden reply came about this word that why I called her dear since she is not my girlfriend or relative. I was shocked. I have a general tendency to call anyone dear without thinking of the sex or age of the person.
So a firewall was being constructed there. I gave my clarification to her that you are like my other friends or relatives or any one else on the earth to whom I love and being a girlfriend is a far away thing. She accepted my feelings and still she is on my contact list. Even being firm on my principle I fear to call anyone dear, I have formed a firewall around me during chats.
Yes, why the love word is used here should not be a question.
Although it does not take more than 10 minutes to be accommodated with a new place or person may be it’s due to my inherited nature. I can be like a family member within 24 hour in any family I enter as a guest or friend.
But when I see reservation regarding the distance being formed, I can feel a firewall. But many a times these firewall I have succeeded to put water and vanish. But I think why I fail to see the firewall around people? And how many firewalls I have to form more as the life goes on?