Alright, I promised myself that I wouldn't talk about this character again, but it's been a talking point on Twitter, I can't get my thoughts out properly in 140 characters, so here we go.
First off, can we all just stop the name calling and snide comments when you see a person/group whose opinions of two "similar" characters are completely different? It's a great opportunity to discuss the differences between two characters, not one where you can act like it's some sort of playground squabble. This is supposedly the "mature" Thomas fanbase, and people should start acting that way.
Back to the question at hand: why is Vinnie being given constant hate? I've already explained my reasoning in his character analysis, but since that isn't enough for some, I shall simply use one word to state why Vinnie is a terrible character and Sailor John, Diesel and the like are: charisma.
Sailor John is one of the best antagonists that the show's ever had because of this. Sure, he gets more serious as time goes on. but you're so invested in his plan succeeding by that point that it makes him great. He wouldn't have been as great if he wasn't able to manipulate Thomas the way he did or if he wasn't so humorous at times (sure the "disguise yourself as a poster" joke has been done many times, but it's still pretty funny in Lost Treasure).
Diesel is still regarded as one of the best antagonists the show's ever had because he has bags of charisma and character. From his nasally, oily voice given to him by Ringo to the slightly less nasally, but more jovial, voice from Michael Angelis all the way to Kerry Shale's voice nowadays, you just hang on his every word because his voice is just so mesmerising that you can't not like him.
When they first arrived, 'Arry and Bert were terrifying. Granted, you had no idea why they wanted Stepney dead (probably just relying on the "they're diesels, Stepney's a steam engine" thing), but they were so menacing and calculated that they were liked by a lot of fans who are now disappointed that a) they do very little these days and b) they left such an impression here that anything else just pales in comparison.
Hell, as sick as it makes me, even Diesel 10's portrayal in Thomas & the Magic Railroad made him a character that many fans liked because he was really well voiced and downright hilarious in certain scenes.
Sharon Miller understood this (to an extent) in Day of the Diesels, which made him the highlight of a special that was, in hindsight, boring and unpleasant to watch in other areas.
And I'll keep praising it until I'm turning in my grave; James was a great antagonist in Tale of the Brave. Sure he wasn't as menacing as the ones I've already mentioned. but he knew how to push buttons, he was intuitive in trying to get his own back and a few of his scenes were rather funny.
The only uninteresting antagonist that we'd had before is D261, who added nothing new to the table and was so uninteresting that he was only in half the episode/story he was in.
Compare all of them to Vinnie, and maybe then you'll realise why he sucks. I'm not saying that putting a bully on TV is a bad thing - they are, sadly, a part of life that we all have to deal with. But just because they're on a TV screen and not next door, at school or wherever, it doesn't make him any more pleasant to watch. Difference is great, yes, but that can be turned to say that Vinnie could've been a different kind of bully.
Tie his attitude into the story and we'll root for him. Give him a legitimate reason to throw his weight around (besides being big and because he can) and he'd have left a less sour taste. Maybe have Philip intentionally get in the way so that Vinnie had a reason to be angry. Or just give him some charisma that made the antagonists I've mentioned so great!
Bottom line is this: if you like Vinnie, fine. Just don't go around acting like him towards those who don't (and vice versa). Liking different things is what makes the world diverse (and I'll give Vinnie that much) and interesting, just don't act like someone should be in the wrong over a God damned opinion. Discuss them, don't deride them.