Why can't I uninstall safari and start fresh. I've been hacked by http://pcsupportadviser.com and it's made safari completely useless

Please specify why do you think that you was hacked by them? Did this website block your Safari browser? If yes try to force quit Safari and relaunch Safari while holding down the shift key.

This is a scam.

1. Force Quit .

Press command + option + esc keys together at the same time. Wait.

When Force Quit window appears, select Safari if not already.

Press Force Quit button at the bottom of the window. Wait.

Safari will quit.

2. Relaunch Safari holding the shift key down.

3. Turn off wifi and turn it back on.

Turn off Wifi. Click Wifi icon in the menu bar and select “Turn Wifi off”.

Visit another website.

You won’t have internet connection.

Turn on Wifi. Click Wifi icon in the menu bar and select “Turn Wifi on”.

Select your Network.

You are welcome