I'd be tempted to heat up a crank spanner and put it over the bolt (melting the plastic), remove the crank bolt and get a bit more room, you never know the dustcap might come with it
I removed a plastic cover by heat & water! Fag lighter to be exact, placed the bike on it's side, then held the lit lighter to melt out the plastic, then threw cold water on the plastic to shrink it quickly, came out far earier with no bashing of tools that would have caused damage in the end.
I have had this problem myself a few times. Use an Awl with the smallest sharpest point you can find. Jam it into the plastic and unwind it out. it usually comes out as a complete thread. A spray of WD40 before you start helps to ease things.