On the internet it's common to see people make arguments that, while having no evidence or logic supporting them, get a lot of praise because they simply appear reasonable. However, there is no reason to assume that they are. Here is a couple:
The "only a few bad apples" argument. This is perhaps the most common one. I think the film Spotlight did a good job of showing how stupid and harmful this assumption can be. People had this attitude towards stories of Catholic priests molesting children, and yet it turned out that while it was only a minority of priests committing these crimes, they were nonetheless a minority which was scarily large in number, and their crimes were being systematically covered up by the organisation as a whole. The problem with the "few bad apples" argument is firstly that people generally either make it because they know nothing about the subject (but it sounds reasonable), or because they are trying to defend themselves and the group which they are part of. Secondly, the statement is entirely vague and ambiguous. How many is a few? Just how bad are these apples? And how many of the other apples know about the bad ones but purposely make an effort to hide their actions? Because I'd say those who do that are "bad apples" too.
The "few bad apples" argument is essentially the same one people use when they say things like "well, most Muslims are probably moderates". First of all, without context, the term "moderate" is meaningless. What context are we speaking of here? Are most Muslims moderate in terms of the general political views of people in the UK? Are they moderate within the spectrum of views held across the entire Muslim population? Or are we talking about moderate, for example, within Saudi Arabian society? Because in each of these contexts, "moderate" means quite different things. Secondly, do we have any evidence that suggests that this claim (whatever it actually is) is correct? Why is this claim routinely considered so much more credible than the claim that, in fact, most Muslims are not "moderates", even if the former claim (whatever it is actually claiming) usually comes with no evidence to back it up. Because without evidence it is in reality no more reasonable than the second claim. Thirdly, the problem is that shrugging off Islamic extremism by saying "oh well, most are moderates" isn't really an adequate response to a serious problem that evidently exists even if this statement is true. Lets say only 1% of Muslims are extremists (and I mean extreme within the context of the general spectrum of views held by people in the UK). That's 16 million people; surely one of the largest groups of extremists in the world.
Another "reasonable" argument people use is usually something along the lines of "oh well, there are bad apples in every <insert demographic>". This is about as reasonable as responding to someone concerned about the dangers of bare knuckle boxing by saying "oh well, people get injured in every sport". Because, while that statement may be true, it is also completely irrelevant. The fact that there are a few bad apples in every large demographic is a given; it simply does not need to be said because we can assume that this is almost universally understood. What is a concern is when there are significantly more bad apples in a demographic than normal.
TL;DR Don't fall for completely baseless arguments simply because they may appear reasonable.