Just read a mostlymissiledefense.com article on the implications of the under development SM-3 block 2A BMD interceptor (
https://mostlymissiledefense.com/2016/06/30/strategic-capabilities-of-sm-3-block-iia-interceptors-june-30-2016/). Once fielded, this 2A variant is also scheduled for deployment to Aegis Ashore sites (starting w/ the Poland site in 2018) as part of phase 3 of the EPAA (ref: CRS 05/26/16 report "Navy Aegis BMD Program").
Unlike the block 1A and 1B version of the SM-3 missile, the 2A variant will have a burnout velocity around 45-60% greater than the assumed 3-3.5 km/s velocity of the 1A/1B (ref: CRS 04/19/11 "Navy Aegis BMD Program" report, and FAS "2011 Missile Defense Report":
http://fas.org/pubs/_docs/2011%20Missile%20Defense%20Report.pdf). This higher burnout velocity is presumed to give the 2A variant a coverage of around 2400-2500 km per the FAS report.
As for the interception target profile, the mostlymissiledefense.com article posted the following image taken from a 2007 MDA BMD briefing:
In the image the 2A missile is credited w/ the ability to intercept ICBM targets during part of the ascent (post-boost) phase, as well as part of the descent (prior to re-entry) phase.
Given this intercept profile capability, together w/ the range coverage data in the FAS BMD report, it would seem Russia's concern could be that, once equipped w/ the 2A interceptor, the Aegis Ashore sites pose a threat to the value of their strategic nuclear arsenal's deterrence capability (both the FAS report and the mostlymissiledefense.com article posit this as well with regards to interception during the descent phase).
In a similar manner in which Aegis BMD ships (pre-positioned near the US) equipped w/ 2A missiles can be used to intercept ICBMs during the descent phase (prior to re-entry), the Aegis Ashore sites (in Poland/Romania) w/ 2A interceptors can be used to intercept ICBMs in the ascent (post-boost) phase. In both cases, the deterrence value of Russia's strategic nuclear arsenal decreases as a result of the BMD coverage provided.
As for the supposed "offensive weapon" threat the sites pose, the voice-over translation for Putin in the video of the RT news article (
https://www.rt.com/news/344642-putin-visit-greece-tsipras/) actually doesn't even use the word "offensive", all the voice-over translation says is "rockets of x range". It's also interesting to note that the range of "2400 km" for the rocket stated in the video coincides quite well w/ the FAS report's estimation of the range coverage for the 2A interceptor.