Speed bumps will only cause damage if gone over too fast - or rather not gone over slowly enough (which may be ridiculously slowly, of course, but damage can be avoided). They are a necessary evil in some locations, though there are probably too many. There was a company I came across who were trying to make speed bumps that went flat if you are travelling at the correct speed. However, it proved technically difficult to make them robust enough, and they were having problems. I do suspect that your e-mailer may have been trying to get something in writing from you to cover him to some degree for causing an accident through losing concentration.