Install this plugin if you want avoid that horses touch on your server.
Fighting on a horse and the other players just glitch through your horse? Not anymore!
The question is not WHY. It is WHY NOT!
Features
Horses can't touch and explode if they do
Set your own touching radius
Save exploding (no blocks or other entities get destroyed)
Select the worlds where horses explode.
Random launches in all direcions
Commands
/ehorses: Displays all commands for explodinghorses.
Permissions:
explodinghorses.commands: Allows to use the ehorses command
Config
radius: Sets the touching radius of the horses.
world-restriction: If this is enabled horses explode only in selected worlds added by the /ehorses addworld <world> command.