Dangers of Qiyas without proper knowledge

This weekend, I had a discussion with a couple of friends regarding a Hadith about forbidding the filing of teeth, plucking of eyebrow and so forth.

There were some speculations as to whether it means whitening of the teeth and so on are also forbidden.  I stopped the speculations because of a few concerns I have with such a discussion:

1. Do we have enough knowledge to know whether the Hadith is muttawatur or ahad; and also sahih or hasan or daif?  

2.  Do we know the background of the Hadith - in what context it was said and the cause of it?  What is the underlying meaning?

3.  Were there other hadiths or verses of the Qur'an supporting or contradicting this one?  If contradicting, how do we reconcile them?

3.  When those are clarified, we then need to understand what is the 'basis' for making the qiyas (extrapolation) to other things such as whitening of the teeth etc?  What is the operative cause/reason for the qiyas?

4.  Could there be extenuating circumstances that may lead to different conclusion?  

5.  What is the impact of making the qiyas?  How wide ranging is it in terms of individual and community level?

 As I learn more about Islamic jurisprudence, the more cautious I become in these kinds of discussions.  Personally, I think we were not equipped to address the above points.  

For example, take the third point...what is the underlying reason for forbidding the filing of the teeth?  Is it because it is not healthy or because it is tempering with what God gave you or it is to beautify oneself or it is misrepresenting oneself to others?  And then we ask how do we know that the underlying reason can be applied to the other activities?

The danger is then that we apply the wrong reasoning and therefore the wrong qiyas.  In that case, we are misrepresenting what the Prophet s.a.w. intended.  And given that we didn't apply due diligence, we couldn't even say that we exercised our ijtihad.  Thus we fall into the danger of assuming a role of authority without being duly qualified for it. And in so doing, interpose our will over the Divine Will.

This little incident is just one example of how I realise, in my arrogant youth, I would have jumped to conclusions that could have had me assuming an authoritarian role in interpreting the Hadith and applying it willy nilly to what I saw fit.  Inshallah, I have learnt my lesson that my knowledge is too limited for such a task but that I should learn more towards equipping myself with the knowledge.

Wallahu 'alam.