The same case as in what happens if someone kicks the ball right into your face in the penalty box ? are you not allowed to use your hand ? Or should you just receive the consequence of having a concusion ? Then any opposition will be smart enough to go to the penalty box, just blast the ball randomly, hopefully a player will protect some part of their body (vital ones especially) with their hands and appeal for a handball.. This is surely not very hard to understand right ?

These things happen everytime in almost every professional football match and a good ref will surely understand the concept well.