Why it is so hard considering solipsism wrong? 

If even accepting that super-dubious statement of that 'The only thing i know existing is my mind'[1], and even further, accepting (blindly) conception of 'All of world can be my illusion', and then realising not all of world is directly controlled to you you think there's 'BUM'. But stop, you CAN'T know whether 'BUM' exists. Then, solipsist say 'world is my illusion' but HOW can one know IF the illusion EXISTS? If we state, that the only thing EXISTING is your mind, you can't go then stating something else exists, like even works of that mind. If you state [1], you live in nothing, but how parts of nothing can be different to each other?
But since you get 'The only thing i know existing is my mind' statement, and 'I think, therefore I am' conclusion i can ask four questions:
-Why if I THINK, then i am?
-Why it is stated that I THINK?
-Why I KNOW my mind exists?
-Why i know that my mind EXISTS?
those can be summed with:
-Why is my mind is supposed to be the ONLY thing to exist?
-Why i know only one thing exists?
-Why my mind is that the only thing existing? etc
As you can see, solipsism is unable to answer any of these, as it is only concerned about those statement and conclusion.  82.209.225.33