Since I am strictly a G1'er, I look back on those days with utter fondness and love it. But you can still be truthful about things: the G1 series was strictly to sell toys. The writing wasn't great, the animation was okay, but also not great, etc. It's okay to say these things while still holding it close to your heart.
Nowadays, cartoons in general have better-written stories that tend to go deeper than what we had in the 80's. That's a great thing. TF Prime is the only TF series I've watched besides G1 (and the crappy Bay movies), and I expected to hate it outright. But I don't, even though there's plenty I still don't like. While I am not crazy about some storylines, at least there seems to be more of an effort in the writing and an ongoing theme. Back in the G1 days, the only impetus for a story was that a new toy was coming out.
So I can see people not liking G1 for those reasons. All the above reasons to not like G1 existed, but still the good far outweighed the bad. So I would still argue against most G1 bashers, because they are wrong.