Why is the planet pluto not a planet anymore?

I agree with the person above - the planet Pluto was considered to be quite small to even be called a planet. After scientists found objects in space which were similar in size to Pluto (and were not planets), they questioned the "planethood" of Pluto. After that, it became a dwarf planet, and not just a regular planet. 

Idisagree because it would have harmed our whole society. starting from the madness of the civilians to the mass destruction of towns.