How to deal with people who are constantly negative and critical

You might have experienced something like this:

You plan a trip, let's say to the Dominican Republic.

The person who constantly criticises says, did you think about this thoroughly, it's too hot there in the summer, the food is not that great, etc.

You say: I am taking a sewing class next week.

Some people say: Oh my God, you can buy clothes everywhere and cheap too. I think that is ridiculous.

And it constantly continues like this. Most people probably expect some kind of defence, however if you react totally differently and just say "Thank you for your tip, I will think about this", it will surprise them and hopefully they won't say things like that again.