Not really - it certainly is wrong to say that because some other country has done XYZ, so now my country have the right to also do XYZ (where XYZ is commonly agreed to be be bad, such as wage war, genocide etc).

Some country might feel that they're justified in what they're doing, because another country previously have done it (and got to a dominant position, perhaps, by doing it). But generally, i dont think this justification is sound, and is an excuse, rather than a real justification. Now of course no country require justification to do what they wish - that is the meaning of having sovereignty, but this also means that other countries must actively stop this sort of practise.