....because it is not physically harmful does not necessarily mean it should b done...
Many things are not phycsically harmful and should not be done e.g. worshipping idols etc.
Ummm what is wronge with worshipping idols if you are not a christian? I don't think it is necissarly a bad thing to mastarbate, It is definately preferable to going out and sleeping around as soon as sexual maturity is reached which for some girls can be 10! For guys it is also probablt preferable to the embarassment of wet dreams. Generally it is probably a matter of taste some people want to some people don't what ever they want in this case it harms no one and some people want to. If they want to go for it I think.
To be honest I don't think that there are any arguments against it!! Nothing but positive stuff. Bloody good fun and reduces chances of testicular cancer! Fantastic!