Use a piece of nylon string or fishing line to "saw" through the old tape. I prevents scratches, and potential heat damage.
Do this and add goofoff to the mix. I used heat the first time and it just made everything messier.
Just take a long piece of monofilament, double it over and twist it, then "saw" behind the badge until you can pul it away with your fingers then SLOWLY peel it right off. Slowly pull the adhesive off (sometimes it'll peel right off, leaving almost nothing behind) Then squirt some goof off on a rag and rub away, the crap will pretty much "melt" off.
I tried heat, WD-40, a plastic scraper, and LOTS of elbow grease the first time............ WAY TO MUCH WORK, imho.
Oh.... and I already gave my badges away, SORRY.