Call.  He can definitely be bluffing or be value betting top pair/overpair/worse trips. He's unknown. Folding strong hands is a losing play.

Not sure what the "right" way to defend this board is but I worked through it and here's what I got:

Flop:

11.3% raise: 66/22, Q-high or lower flushes, some AdXx, some connected cards near the 6 or J with one diamond in them

42.2% call: all pairs, Q-high or better flushdraws, A/K-high made flushes

46.5% fold

Turn 6s:

I'm not sure about raising here. Our nutted hands got slightly worse on this card since I raised sets on the flop but our overall range advantage vs his improved because we have more 6's in our range I think. I wouldn't expect him to bet that often here and when he pots we can fold a lot of stuff. On the other hand if he mistakenly thinks he can have a wide betting range here we do benefit a lot from making him fold his equity because he has a lot of flushdraws and we have a lot of trips. I'm going to ignore the idea that we could raise a lot here because I'm not comfortable with it in a vacuum and we didn't in the actual hand.

50.3% call: J9+, J8d,J7d, AdXx, 8d8x 7d7x.

49.7% fold

River 8c:

53.3% call: 2p+, KdJx, QdJx.

46.7% fold

so yeah, our hand is definitely a bluffcatcher but comfortably in the range of hands we have to be calling with. I think we could plausibly be folding some trips on the river if we never raised the flop or turn but given we have a raising range on at least one of those streets they'll end up easily making the cut for our river calling range, and also trips with the Ad are like, always going to be one of our best bluffcatchers.

One thing we could do is defend the turn more than 1-A and the river less than 1-A. That way we could make it so he's still incentivized to bluff turn in order to follow through on the profitable river bluff but we get to jam our trips for protection and jam some good semi-bluffs with them. I think that this could work theoretically at least.

You're getting 3:1 to make a river call so even if you're running into the nuts here, he should still have enough bluffs in his range to make the call +EV.