In attempts to discuss my beliefs with some people in the denominations, the issue of alcohol came up (the person I was speaking to brews her own beer).
Their claim was that Acts 2:13 proves that the new wine was alcoholic, even though I tried to point out that, instead, it was being used as an insult by the mockers. From that belief, they argue that all new wine must be alcoholic, and thus Jesus himself drank. Their other claim was that there was no way that fruit juice would not ferment between harvest and the Passover meal. I know that this is false teaching, but I am not sufficiently versed on this topic to be able to refute such claims.
I know that as a Christian, our duty is to warn against such topics, but in this specific instance, what information do you have that would refute their claims?
The arguments you mentioned are covered in these two articles.
You won't be able to convince a person who refuses truth (II Thessalonians 2:9-12). The argument that new wine means alcoholic is so poor, it is hard to know where to begin. Here is what Albert Barnes said,
"This word properly means the juice of the grape which distills before a pressure is applied, and called must. It was sweet wine; and hence the word in Greek meaning sweet was given to it. The ancients, it is said, had the art of preserving their new wine with the peculiar flavor before fermentation for a considerable time, and were in the habit of drinking it in the morning. See Horace, Sat. b. ii. iv. Sweet wine, which was probably the same as that mentioned here, is also mentioned in the Old Testament, Isaiah 49:26; Amos 9:13."