Reading sociological images I saw the following exchange:

Jessica: Oh my goodness you're right! I never thought about that before. That is lame! ...
REAvery: Please don't say lame as a pejorative; its abelist. I know you probably didn't mean anything by it, but it is not an appropriate expression of irritation or disapproval.
...
al oof: http://disabledfeminists.com/2009/10/12/ableist-word-profile-lame/

This is a common pattern in some parts of the web: use of some words and phrases will get posts/posters 'called out' as ableist/sexist/etc. The standard argument is something like "this usage causes pain to an oppressed group, avoiding this usage is easy, stop using it." For an example of this, see Arwyn, commenting on a post saying that using lame as a descriptor is always ableist:

Here's the thing: it's a teeny, tiny word. It really shouldn't be a big deal: it causes pain to an oppressed segment of the population, and is really easy to avoid using. If people who temporarily have able-bodied privilege think it's such a small deal that people with disabilities shouldn't care about it, isn't it a small enough deal that they could just not use it? What does its avoidance cost you? Nothing. What does its avoidance give to those you profess to care about? Everything. The only people making a big deal out of a small word are those clutching it to their chests, refusing to give it up.

This shouldn't be a hard calculation, people. It's just a word. Just stop using it.

For a single word such as 'lame', this argument makes sense to me: the mental cost is pretty low, and I can see the benefit. Thing is, there are a lot of things one is should keep out of ones speech. Just from ableist word profile series linked above, we have:

crazy, cretin, crutch, febleminded, halfwit, hysterical, I feel your pain, idiot, imbecile, intelligent, invalid, lame, mongoloid, moron, nitwit, ocd, retarded, scab (worker), smart, vegetable (person), weak, what's your problem,

Others that are widely seen as problematic are gay, girl (when used for women older than N years), fireman, etc, douchebag. Now, some of these arguments I disagree with (this is a good counter argument for 'douchebag'), but for many I certainly believe that the term is harmful. For some of them, such as 'gay' and 'retarded', I've intentionally avoided the words for a long time. If I agree that these words are harmful, though, should I dramatically expand my list of ones to avoid? Should I go a step further and start correcting the people around me? I'm not sure that would be good. The argument above rests on the idea that avoiding a word is basicially free. Is avoiding a whole lot of words still free? Or is there a small cost for each word that must be substituted for? I believe that avoiding the word "retarded" no longer takes me any mental energy because I no longer would think to use it, but it took effort to cut it out of my speech in the first place. If I spent a lot of time around people who used that particular word a lot I might still have to remember not to use it. It worries me, then, to suggest that people cut out words that they use a lot and are used by the people around them. I'm not sure how to balance the needs of the people a word negatively affects against the needs of the people who'd be avoiding the term.

(This self monitoring and correction are not just for avoiding offensive phrases. Many people are happy to correct those around them over the distinction between 'less' and 'fewer', the use of 'hopefully' in place of 'I hope', splitting infinitives, and the use of objective case on pronouns in a conjoined subject (me and joey are ...). I'm not sure this is good either.)