"While letters ‘vb’ are quite generic and bear no offensive meaning in themselves, they’re being used as a domain name for an openly admitted ‘adult friendly URL shortener’. Now, had your domain merely been a URL shortener for general uses similar to bit.ly (as you claim) there would have been no problem with it. It is when you promote your site being solely for adult uses, or even state that you are ‘adult friendly’ to promote it that we as a Libyan Registry have an issue."
There is definitely some risk, so mitigate it and buy the ly.com variant of a .ly domain to protect against this - much like ad.ly owns adly.com, embed.ly owns embedly.com.
Watch what bit.ly does - likely nothing right now. If they get warning like vb.ly says they did, we will hear about it, and then every .ly owner has a problem.