Is it permissible to use the internet at the place of a Rafidi person who curses God and exploits government fuel, knowing that he allows it for free and in his absence, with the intention of using it for a good deed?

It is not permissible to browse the internet in someone's place without their permission, because it is consuming their wealth unjustly. This applies to the wealth of both Muslims and disbelievers. It is obligatory to forbid and rebuke anyone who curses Allah Almighty, for cursing Allah is the gravest form of disbelief. It is also not permissible to steal his money.