+1 on the above, DO NOT use the rear set as a vise.
I bought my bike used (and wrecked) and have straightened the shifter lever (same material) in a very heavy vise with a 5 lb hammer.
Even if you don't have a vise, scroung up a hammer, a solid concrete surface, some thin aluminum (to protect the finish of the lever) and POUND away. That lever is
very sturdy and CAN literally take a beating without breaking. Just don't smack the splined end..
Obviously, clamping it in a vise would give you more control over it and give you better results (straighter, etc).
As to the original question, will you hurt anything on the bike, no. The brake light switch will remain off (no rear brake pedal, brake light), just the possibility of you, in an emergency, going for a lever that isn't there
