Evolve bagon?

Yes, evolve it as quickly as possible, don't think twice

Transfer, it's IVs are horrible.

Just kidding, and congrats on the great hatch. Evolve it, and hope for the best. (DT/DM) If you get a 95% IV or above from an egg, save it for community day where it may get Outrage and destroy all the non-legendary Dragons once and for all, as well as more than half of the legendary Dragons. (Sad if you really think about it)

I think there's a lot to consider here. Ultimately, the reason to not evolve would be to evolve it on a community day instead (and hope for outrage or another better move).

It's quite likely Bagon will have a community day - possibly as early as December.

So consider:
Do you expect windy weather to be possible on Bagon CD (to get them weather boosted)?
Do you play with other friends, will you be able to trade the Bagon's you catch on community day to reroll IVs / look for luckies?
Do you play "hardcore" on community days?

Ultimately, if you expect to get better specimens to evolve on Bagon CD, then there's no harm in evolving it now. If you don't, you'll have wished you waited.

As a rough comparison: I played in windy/snowy weather on Beldum day and made ~50 trades with a Best Friend for 3 lucky Beldum. I evolved 8 in total (6 regular, 2 shiny), 4 of the evolves were better than the listed Bagon's IVs (one similar, one slightly worse, both shiny much worse) and all at level 30+ except one of the shiny.
If you have similar experience - no harm evolving now.

Another player commented on these boards that his best was something like an 84 with 15 attack at a low level. If that's generally your experience - then you may want to save this one.