Anything where you bang, smash, or generally try and muscle the arm off will probably damage the BB as well. I recently used a homemade tool to get the arm off my triple drive side and preserve the BB. Worked like a charm.
If nothing else works I made a tool but it requires drilling 3 holes through the crank arms. I use a park tool and drill matching holes through a large washer.
1) Drill 3 holes through a large steel washer. Select the washer that has a hole that will brace a park tool crank remover. If you can't find one then use 2 washers of different sizes.
2) place the washer over the crank arms and drill pilot holes. Note: depending on the crank arms you may need to use 4 holes.
3) Separate the arm from the part you normally screw into the crank arm and place the washer(s)on the lever arm bolt. screw into the mounting part.
4) Use carridge boles and pass through the washer and the crank arm. secure the nuts on the carriage bolts using washers.
5) Using the washers to brace the park tool turn clockwise to remove the crank arm like you normally would and voila...the arm will come free. Note: the sizing of everything will be important.
Good luck.