You should. Everyone should. Mine is just one man's opinion (mine), and I don't try to convince anyone it's worth any more than that.
Head-Fi is a niche, and given the number of sponsors here, many of the products we discuss on Head-Fi happen to be sponsor-made products. I imagine, then, that this instills doubt with you about much of what I say. I understand that, and I can live with that.
I don't lie about my opinion. I don't say I think something sounds good that I don't think sounds good, sponsor or not. I don't say I think something sounds great that I don't think sounds great, sponsor or not. So when, in two videos (and in the upcoming gift guide), I said that I think the Stax SR-009 is the best sounding headphone ever made (to me, based on what I've heard, and my preferences), I said so because that is indeed my opinion.
And Stax isn't a sponsor. Never has been. I don't believe they've ever bought any type of ad here. Which means I think a non-sponsor's product sounds better than anything currently (or ever) made by our sponsors, and I've said as much several times.
Still, I don't expect you or anyone else to value that as anything more than my opinion, for whatever that's worth to you (if anything at all).