When the people of Israel sinned in the notorious golden calf incident, Moses responded by grinding their idol to powder, throwing it into the water, and making them drink it. They drank the object of their foul worship, thus becoming completely identified with it—in that case, for cursing.
We also consume what we worship, partaking of Him by faith. Jesus Christ suffered, bled and died on the cross, shedding His blood for us. This cup is the cup of the new testament, and Paul calls it the cup of blessing. We drink wine that represents the blood of the one who died for us. The Israelites in the wilderness drank the defiled water, made up of the remains of the idol who was going to consume them.
We drink death followed by resurrection. They drank death, and that was it. We drink death offered for others. They drank death that was simply the fruit of their own sin.
We drink from the rock that accompanied the Israelites in the wilderness, and that rock is Christ (1 Cor. 10: 4). They drank from a stream that was from God also, but it descended from the mount, and was a bane to them (Dt. 9:21).
If you are worshipping an idol, it does not matter that you say that your festival is to Yahweh. The dust of the idol is thrown into the drink, and you become more and more like what you partake of. But this is not what we are doing here. We have come before God with true faith in Christ, and we trust in Him alone for our salvation. We look to Him alone for the forgiveness we all seek. We do not drink judgment in the water; we drink forgiveness in the wine.