Every thesis has an argument. In order to argue something “new” or “original” you need to know what has been argued before and where you can go with your own research. There is a certain kind of thesis, a very common one, which is largely a negative argument: Professor So-and-so’s theory on X in respect to Y is WRONG. Or, perhaps a lighter version: My solution to the problem Y is correct, which means that Professor So-and-so’s theory is WRONG.
Theses like these are often times very interesting and can have the power to shift consensus opinions. These can often be very fun to read and can be persuasive if the evidence is there. Once you have hooked your reader (in the first couple of chapters), he or she often buys into it and is waiting to hear more in your subsequent chapters.
The problem comes if the writer has an us vs. them approach. This can even become ad hominem where the goal of the writer is to lampoon the opposing position. There are a few problems here. The first is that your viva examiner(s) may not feel persuaded by your very one-sided approach (especially if it is unrelentlessly antagonistic and vituperative). Secondly, I am personally put off by someone who treats their scholarly debators as punching bags using words like ‘absurd’, ‘clearly not’, ‘obviously’, ‘ridiculous’, ‘a very poor attempt to…’. If we have read the appropriate literature on both sides of the ‘debate’ (whatever it may be), you show a certain air of intellectual superiority and academic ignorance when setting up your opponent as a fool.
How can you avoid this? Be careful when the temptation comes to use polarizing words like all, never, always, etc…These kinds of statements can seem clumsy. Also, when you seem to be setting the opponent up as a straw man and/or a whipping boy, it can make you come across as intimidated and insecure. Be willing to highlight what you agree with in the work of your debators.
This us-versus-them seems to be a tendency that is more common amongst conservatives who sometimes appear to have an axe to grind. If you are a conservative (as I could be labelled), this may be something to keep in mind when you formulate your thesis idea and decide whom your debating partners are. Remember, it is a debate, not a lynching. Your goal is to win the argument and further a better understanding of the text – not to stand victorious over the bloodied bodies of your ‘enemies’.