Baptists*, in particular, are fond saying "We have no creed but the Bible."  As [this wonderful video shows, that *is* a creed](https://www.youtube.com/watch?v=GPg0wBP5k6M), but it gets to the heart of your question - why do Baptists view creeds negatively?  [*Really -  go watch the video. It does a better job than I will of explaining the reasoning, and debunking it!*]

There is one scriptural reason and one legacy:

1. Baptists have a very [particular notion](https://christianity.stackexchange.com/q/24484/1039) of 'vain repetitions' as used by Jesus in [Matthew 6:7](http://biblehub.com/matthew/6-7.htm). Even [the Lord's Prayer](https://christianity.stackexchange.com/q/7098/1039) or the [liturgy](https://christianity.stackexchange.com/q/14109/1039)--anything that smacks of 'saying the same words without any meaning behind them'--is taught against regularly in Baptist teaching. As such, there tends to be a distrust of anything liturgical.  Along those lines, some will also add [Paul's bit](http://biblehub.com/1_corinthians/3-4.htm) about some following Paul, others Apollos, and other 'Christ.'

2. The simple fact of the matter is that 'credalism' or 'confessionalism' as you prefer to put it, is really a mask for a greater issue - namely, Baptists have a very significant distrust of Roman Catholicism.  This [distrust](https://christianity.stackexchange.com/a/8304/1039) has [historical roots](https://christianity.stackexchange.com/questions/23023/what-is-the-historical-and-theological-basis-for-protestant-anti-catholicism) and is often taught using the concept that 'traditions' are less 'good' than scripture. (We won't get into the fact that how one reads scripture is a tradition.)  This manifests itself in the ['Trail of Blood' rhetoric](https://christianity.stackexchange.com/q/9986/1039) and has a long pedigree.

As you can see, even as a Baptist, I don't put much stock in these arguments, but they are deeply engrained in the teaching.

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*Just to clarify, I'd suggest that a big asterisk go on "Baptists" here.  This tends to be the view of an older, more fundamentalist strain of Baptistic thought than what is probably the mainstream today. I use the word here to denote what types of protestants are most likely to meet your criteria, moreso than to argue the point for the whole. That said, I don't have any numbers either...