why does my ford focus oil filter keep on blowing rubber out?

Many times the old oil filter gasket sticks to the motor flange and then the oil blows out from in between the two gaskets.

Are you tightening the filter more than half a turn after the gasket contacts the seat?

The oil filter is under pressure, the oil pump develops that pressure. There is a regulator for the oil pressure, it must be stuck closed creating far too much oil pressure. Test oil pressure, you'll find it way too high. Find regulator and repair.

By far the most common cause is the remains of a gasket from an old filter stuck to the engine.

that is normally caused by a stuck or broken oil pressure relief valve. other cause may be wrong filter / O ring but unlikely or failing to tighten filter.though in practise these only need to be turned until they touch flange face and then one and half turns by hand. ( never use wrench to tighten unless with a torque meter set at the low values needed)
if we unsure or unable to change relief valve ( often part of oil pump assy) have a garage do it for you.

There could be an obstruction in the oil passages in side the block. If this were the case there would be other symptoms like valve clatter.
Most common cause is that the previous gasket was not removed.
Second cause is failure to tighten the filter correctly. I use "contact" (between the gasket and seating surface) plus 3/4 turn by hand.

Check and double-check if you have the correct oil filter. When installing, tighten the filter only hand tight. Do not use an oil filter wrench. Issue does not go away. call a shop.