If someone tries to sound smart in repartee by saying,
Well obviously blah blah blah
but what they said is actually wrong, then what's a good comeback to that, or what's a good way to phrase the comeback?
Simply questioning the statement comes right to the point. You didn't actually say that you were looking for a witty comeback. Just that you wanted a good response.
You can always add:
How can it be obvious, seeing it is false?
And I would agree with you, except we would both be wrong.
Someone overeager to sound intelligent is likely to enjoy going into depth. Simply asking "What do you mean?" or "Can you explain it further?" is a good way to keep them talking. If the details in their obvious point start breaking down it should open the discussion up for a direct counterpoint or counterexample:
Obviously blah blah.
What do you mean?
Blah blah blah.
What about [example]?
Blah blah blah.
[Backpedalling goes here.]
The real wit here is that a group of intelligent listeners will likely notice the inconsistency before the speaker does. If they care enough, they will continue the line of questioning for you and the original statement will be dismissed as a falsehood.
If what they said is wrong, there no need for a witty comeback, LH. Simply point out that they are mistaken and be prepared to substantiate that.
Well obviously you're clearly mistaken
Well obviously you've not checked your facts
If you're sure they're wrong, then stare them in the eye and say
Obviously Not, ...
or you could be nasty with
"Yeah, obvious to one who talks out of his a$$, but for the rest of us .."
The right response depends crucially on what you want to achieve. The most common mistake people make in this situation is to miss the big picture and want the wrong thing.
You asked for a comeback, which suggests that you want to look good, gain the admiration of other listeners, and puncture the speaker’s ego. I don’t know the context, but I’m guessing what you should want in this situation is either to quit wasting time in an argument that nobody is going to learn anything from, or else to cool off the discussion and get it pointed in a productive direction.
To do that, first check to make sure your body language, facial expressions, and tone are friendly and not confrontational. Then, ignore the word obviously and politely address the substance of the argument instead.
(This question is tagged repartee, which suggests a totally different goal. But repartee is a witty exchange; it takes two to tango, and your stereotypical obviously speaker is not going to be a good dance partner. Judging by these answers, a global community of StackExchange users is not a very good dance partner, either. Zing! ;-)
Another one to kind of stop them in their tracks might be to simply interject prior to them finalizing their assertion with:
Actually... or Not quite...
If we take into account different circumstances, for example, in an instance where what is being considered might seem obvious even if in fact incorrect, then a less abrasive approach might be:
Well, naturally one might think so, however...
Each of which is to be followed by a short, concise flurry of information that makes 'no bones about it.'
Come to think of it, there's another reply you could use based on the above reference; maybe witty, albeit a little irrelevant to the target given that it might not be read into:
I see bones in it... (or some variation of)
An overview from the above link:
This is a reference to the unwelcome discovery of bones in soup - bones = bad, no bones = good. If you found 'no bones' in your meal you were able to swallow it without any difficulty or objection.
What makes it obvious?
Ask them to explain further, and question until they realize that their point is NOT obvious, and even incorrect. Ask in a non-sarcastic manner, as one truly not understanding why it is obvious.
You say, "I don't believe that you know what 'obviously' means."
Well, obviously blah blah blah…
Such and such may seem obvious to you, but [counter point].
A polite and productive answer could be
"I hear what you're saying and agree it sounds obvious, but what about if..."
After validating the person's ego like this, he/she is more likely to respect you and listen willingly.