What do we do if SETI is successful?

As a pragmatic opportunist

- Setup a massive array of antennas in space for reception only

- Try to decode their radio traffic and understand how they are exchanging information

- Steal their their knowledge and use it to advance human race forward.

- Reduce all our electromagnetic emissions to minimum to deny them the same advantage. Forbid anyone from sending signal towards them so we have time to technologically catch up to them without them noticing.

Any kind of contact will ends up in abysmal disaster as we have seen in the past, when advanced civilization shown up on shores of less advanced one.

This presumes they have the same nasty survival-of-the-fittest kill-or-be-killed attitude as humanity. Our evolution kinda created that but it doesn't have to apply everywhere. I think it's entirely possible that alien civilisations could exist that are a lot more symbiotic.

We have a saying in Holland "the innkeeper trusts his guests like himself" which seems to apply here.

>Our evolution kinda created that but it doesn't have to apply everywhere.

Presumably any alien species was also shaped by evolution, so is also likely to be similarly competitive. Maybe you can escape your evolutionary past. But maybe not.

They'd have to get through The Great Filter, so maybe they'd have avoided or have moved beyond some of our evolutionary downfalls.