So maybe, just maybe, you shouldn't "grab a wheel" of someone you don't know, outside of a group ride. You have no idea what they will do. If you cannot safely stop before plowing into the rider in front of you because you are following too closely, who may or may not know you are there, in any situation that happens it is 100% your responsibility. That's a risk people agree to take in a group ride. Don't assume random strangers want to take it too. It just makes you an ass.

Now in a group ride there is no excuse for an unannounced sudden stop, short of an emergency. If you don't want someone behind you, don't go on group rides.