I would tend to disagree. Though all are words used for the conjunction of thoughts, and thus are similar in scope, each word has a particularity that should be observed by the vigilant writer (or reader for that matter). The exact meaning can be derived from the root of the words, eg, further-more - here 'further' implies to delve with greater profundity, (not to be confused with farther, which is a measure of distance) Thus, furthermore may be used when the second statement complicates or exacts or illuminates the first statement with more precise (more profound) information.
like-wise: here 'like' implies that two statements point to similar conclusions, but are not so closely related as those which would be conjoined with furthermore. ex. John drank some water; likewise, billy took off his shirt. They were both hot. It must have been 100 degrees. Here, furthermore would not do. synonym: similarly.
besides - (beside or aside) this word is difficult to use well, and is a sign of mastery. In non-fiction, it may be used when the author wishes to add to an argument using a statement that does not fit with the tone of the article or one that cannot be justified with the same rigor as the rest of his argument. For instance, if the author wishes to make a quib in an otherwise scientific or professional paper, "george bush is evil because..... ;and besides, he's from texas. " This is of course a terrible example, but great authors have a delightful ability to appreciate impertinent, common sensical or even ironical details without in any way besmirching their argument or discrediting themselves. This is why, as Socrates might say, we must beware of rhetoric! (Again, in such cases, 'furthermore' or 'likewise' or 'moreover' would not do.)