Sometimes the deviantART Help desk receives bug reports from deviants saying there's something wrong with their own or someone else's account because another particular account will tell then they are "deviously denied" (which means blocked), while the owner of said account untruthfully claims there is no block in place.
We'd advise against being dishonest about user blocks, because a lot of the time the blocked deviant will report the situation as a bug as a result of such dishonesty and we will then in fact tell them whether they are currently being blocked by the particular deviant or not.
Personally, I find it rather sad when a deviant submits such a bug report, saying their friend's page is having a problem while said friend is denying having a clue about it, and us ultimately telling the deviant that their friend is indeed blocking them.
From a policy and staff stand-point, you can block whomever you want for any reason or no reason at all and you don't owe anybody any justification for it.
However, when you block another deviant, have the decency to own up to it if the blocked deviant addresses it outside of deviantART (keep in mind that circumventing a block on-site is against our policies) because the blocked deviant can find out about it either way.