From the AP wire…
ARLINGTON, Texas (AP)—So what that the Texas Rangers won their only game this season against Detroit Tigers ace Justin Verlander.
This sentence tripped me up in a couple of different ways. First, I initially had trouble parsing the subordinate clause, "the Texas Rangers won their only game this season against Detroit Tigers ace Justin Verlander." Now, obviously it doesn't mean that the only game this season that the Rangers won was against Verlander. For a little while, I thought it was a muddled way to say that the only game this season that the Rangers won against the Tigers was against Verlander. Eventually, I got it: the only game in which the Rangers faced Verlander this season was a game that the Rangers won. In other words, it's:
the Texas Rangers [won [their only game this season against Detroit Tigers ace Justin Verlander]]
the Texas Rangers [won [their only game this season] [against Detroit Tigers ace Justin Verlander]]
Now that's settled. But what about the introductory "So what that…"? Shouldn't it be "So what if…"?
"So what if…" is a common colloquial opener for a subordinate clause (in American English at least), with the sense, "What does it matter if (such-and-such is the case)?" Note that the if doesn't have the same counterfactual force that you might get by leaving the so off: "What if…?" tends to imply an imaginative leap into a non-existent world. (See Geoff Pullum's "Real debate about unreal worlds" for more on counterfactual conditionals, and his "Questions and conditionals" about the use of if as a subordinator.) Because the subordinate clause can express a factual statement, we could, in theory, use the subordinator that in place of if. At least an alternation between if and that is perfectly acceptable in other syntactic frames:
It doesn't matter if the Rangers won that game against Verlander.
It doesn't matter that the Rangers won that game against Verlander.
Who cares if the Rangers won that game against Verlander?
Who cares that the Rangers won that game against Verlander?
So what if the Rangers won that game against Verlander?
?So what that the Rangers won that game against Verlander?
"It doesn't matter if/that…" and "Who cares if/that…" conform to the usual patterns of English syntax, but "So what if/that…" is a more idiomatic construction. I suppose I expect if to follow "So what…" because of the resemblance to the counterfactual "What if…?", but it's clear that others aren't bothered by the that alternation:
So What That You Didn’t Ask (Jo Ashline, 9/26/09)
So what that Barack Obama Saw Avatar, it still sucks!!! (Facebook group, 3/5/10)
Microsoft: So what that Apple is the 'biggest' tech company? We're still rich! (TechCrunch, 5/28/10)
So what that evangelical leaders are divided over tithing? (Generous Matters, 4/13/11)
So what that there was a Hurricane and Earthquake–Adherence is More Important (Law Librarian, 8/30/11)
So what that our thousands and thousands of low-income houses are all rebuilt since the storm. (Sandbar Politics, 10/7/11)
So what that he made her eyes bleed. At least he got the bitch to sob! (TV Fanatic, 10/7/11)
The idiomaticity of so what means that it doesn't have to be treated compositionally as a combination of so + what — freeing it up to be treated as a declarative subordinator like "It doesn't matter (that)…" rather than an interrogative one. There does seem to be some confusion when that is used instead of if, since some of the examples end with question marks while others end with periods (as in the AP's lede) or no punctuation at all. But then again, plain-old so what can end with a period or exclamation point in informal writing, so punctuation might not be a reliable guide here.
Dictionaries aren't much help in making sense of all this. Even the far more common collocation "So what if…" hasn't attracted lexicographical treatment. The OED entry for so (not yet revised for the third edition) covers so what only as a standalone retort and the related attributive use:
10 c. so what?: a retort made to an assertion, implying that the problem expressed has no immediate interest or obvious solution. Also as attrib. phr. orig. U.S.
1934 M. H. Weseen Dict. Amer. Slang 399 So what?—What of it? What does it matter?‥ What does that have to do with the matter? Your remark has no bearing or significance.
1935 F. Baldwin Innocent Bystander v. 83 ‘He has a wife,’ said the girl gloomily. ‘So what?’ asked Angela carelessly.
1938 C. Landery (title) So what? a young man's odyssey.
1949 Hansard Commons 21 Nov. 104 That is unfortunate and disappointing but, to use an American expression, ‘So what?’
1953 in Shorter Oxf. Eng. Dict. (1955) . Add., The tragedy of the ‘So what?’ generation.
1960 M. A. Sindall Matey xiii. 177 She suddenly yawned and flung the magazine on to the seat. ‘So what!’ she murmured.
1968 C. Watson Charity ends at Home x. 126 No, the fact is that Henny and I got along as well as most. Not around each other's necks all the time, but so what?
1970 T. Hilton Pre-Raphaelites viii. 201 Burne-Jones pushed art so far away from this world that our reactions to some of his paintings are of a merely so-what kind.
Despite its absence from the entry, "So what if…" followed by a subordinate clause has been in use in American English for more than a century. For instance, there's this line in a May 30, 1909 Washington Post item about the aging "Buffalo Bill" Cody and his not-so-sharp sharp-shooting: "So what if he doesn't break the glass ball every time?" "So what if…" might deserve attention when the OED revises the entry for so, but I would think "So what that…" is still too marginal to make the cut.