People who have to worry about how others spend their money have bigger problems than money. If you weren't dressing your dog they'd find something else to be critical of. I think you were smart to ignore them. They didn't deserve a reaction from you.
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"If you have men who will exclude any of God’s creatures from the shelter of compassion and pity, you will have men who will deal likewise with their fellow men." — St. Francis of Assisi, 1181-1226