Why so snotty about people wanting to have fun supporting their club? I don't know if you've been to any European aways, but they are the best times i've ever had following Everton.
Aside from that, there are not "dozens of reasons why it is a general bad idea". There is one. Fixture congestion. It might cause us to drop some points or tire out. Or it might not. Just like it didn't for Tottenham last year when they challenged for the League Title while being involved in the Europa League until late March. We'll need to manage it carefully but there's no reason why we can't.
There are plenty of reaons why it would be great to be involved. Increased exposure, increased revenue, attract better quality players, more game time for younger players, European experience for the squad, having another path to the CL, and another chance of a trophy, and boost our Co-Efficient so that we have half a chance of doing well if we ever do manage to break into the Champions League. It might be a nuisance for clubs like Man United who already are a super-power, but for a club like us it would be a big step to help us move forward, and that's why both Moshiri and Koeman outlined it as our target at the beginning of the season.