I have an honest question for you. Have you ever seen a bulletproof vest?
Also, the person you’re replying to gave a very frightening scenario: being hunted down at your own home. If you’re not shooting back, what do you think the enemy is going to do? Give up and go away? Molotov cocktails are an easy, low-tech solution to a barricaded enemy you don’t care about taking alive.
Now, if we assume you’re in public, there are still issues with a bulletproof vest. They’re not really all that great at being concealed. If you truly have a bulletproof vest that can fit underneath clothing, it’s not going to stop many bullets. You can look through the wikipedia page on different levels of body armor, and do a quick search to see how bulky the different types are. Police armor is rated for most handguns, and is super bulky already. Military armor can hopefully stand up to a rifle bullet, but they’re often ceramic plates, which don’t last against multiple rounds, and are very obvious and stand out. Your slim-fit vest may be able to handle a very small subset of rounds. If you go the route of more protection, you’re going to find yourself targeted by the gunman due to your visibility and because your potential as a threat is large compared to others. Even a very high quality, military vest/suit is not going to cover you well enough to make a difference if a single person is shooting at you and A) you don’t have buddies to give you cover fire and make them put their head down and B) space because you knew the shooter was an enemy before he pulled out a gun and started shooting at you.