Target selectors ignore invalid arguments

"@e[customName=Xephos]" works EXACTLY the same as "@e". This causes extreme problems, like when using the "kill" or "tp" command. This caused me to teleport all entities on my friend's realm to one spot. It will take a while to fix this.

What I expected: The command fails due to an invalid argument.
What happened: The command completely ignored the argument, and teleported every entity.