From an article that recommends things to read to help students too focused on exams and disconnected from the rest of the world.
This phrase, He never met a ________ he didn't like, is a "quip" which is used to say that the person in question is indiscriminately or excessively fond of _________, whatever that happens to be.
He never met a beer he didn't like.
He will drink any beer, or he drinks rather a lot of beer. He will never refuse a beer offered to him.
He never met a graph he didn't like.
He is rather too fond of charts and graphs. He will take every opportunity to stick a chart in the body of the text, no matter how unnecessary it may be. Or he will peruse any chart you put in front of him no matter what it presents, he is such a "data-hound".
It could be said of a politico with a hawkish outlook or the CEO of a company that makes military weapons or of a corporation that supplies military logistical support:
He never met a war he didn't like.
It could be said of the stereotypical overweight cop on the small-town street:
He never met a donut he didn't like.
It could be said of a narcissist:
He never met a mirror he didn't like.
A politician who believes in minimalist government, say, or perhaps in "Social Darwinism", might say of an opponent who believes in spending on domestic social programs:
He never met a tax he didn't like.
User Hot Licks adds the following remark (though Rogers may have said something a little different from what has been attributed to him over the years):
It should be noted that this trope probably originated from the expression "I never met a man I didn't like", likely first uttered by American humorist and writer Will Rogers. In the case of Will Rogers it was likely reasonably true, but "never met a XXX I/he didn't like" quickly acquired a sarcastic sense.